You could start by actually trying first.

Cable raceways. Just stick em to the back of your racks, or on the bottom of the shelves and run the cables through em. You might need some you can stick to the wall, if you want, to run cables to the TV. You should also mount the power strips on the shelves, probably the lowest shelf. You can use one if those boxes that conceal the power strips, or use one of those under desk mounted shelves the'that you can put the let power strips on. Along with cables and stuff.

Effort?

For real though, get a roll of Velcro and start there https://amzn.to/3R91Sqd

Like this is very bad, not even trying. Start somewhere, then ask for alternatives.

Do you have attic access over that wall? A really long HDMI/RCA could go from behind the TV into the wall, up to attic, skip a few studs, then down to a brush faceplate behind the consoles

Aye, it's a fucking shit show alright. Hide the cables behind some low wooden shelves under the TV and put all the devices on those shelves (drill holes in the back of the shelves for the cables to go through). Otherwise stick that big black hairy god-awful pimp carpet over the whole lot of it and velcro it to the wall. Also, you need to get a good plasterer. That back wall is a fucking disgrace.

I think what you've got is fine.

Embrace it.

Add a happy cutout of a rat, to that rat's nest.

I've got some suggestions and "tiers" of permanence for you.

Power

First, get yourself something like a vertical rack power strip (like one of these). You can probably notch the shelves to incorporate it well, without adding any required space behind them. This alone will go a long way towards cleaning things up.

Video

This is probably the other biggest mess is the video cabling. Here, there's a few options.

Permanent, upgradeable, but harder to keep neat and probably a bit of a PitA to run cables

Use some cable passthrough wallplates like these. You'd install one close to your shelving and one close to your TV, then fish cables through. Given the distance, there's probably at least one stud in the way that would make it a bit of a pain.

**Permanent, cleaner look, probably easier to run and more expensive **

Use HDMI/coax/RCA jack plates and pull cable through attic or basement. May need active cables to avoid issues (differential pair signaling used by HDMI can get finicky).

Semi-permanent

Purchase or make cable raceways. There are some commercial products that replace baseboard or crown moulding. This is probably the easiest route for clean appearance. You can use the risers in the shelf as anchor points to run up or down to your raceway, if you are ok with visibility there. Otherwise, notch the shelves, like the above suggestion for power, and run raceway/square conduit up or down, with ports for each shelf tier.

Less permanent, more expensive

Get an A/V receiver/mux box that you can use as a central connection appliance for the shelves. This way, everything connects to it and you have the minimum number of cables going from it to your TV. I honestly don't know how much these things currently cost but they used to be pricey on account of being marketed to the "audiophile" segment.

Networking

Try to concentrate as many of your network-capable systems on adjacent shelves as possible. Install a keystone jackplate and either run Cat6 for each device or use a small edge switch and as short of patch cables as you can manage.

You could try starting with some cable management and then maybe move on to more cable management.

Seriously, at the very least why arent these cables behind your shelving instead of draping over the front edge? Thats crazy. Then you have a pc in the middle with cables going both ways. Is that a LAN cable coming from the right? Drill a hole and run that through the wall and either run it along your skirting board or get some trunking.

You can even remove the skirting, cut away a small section from the bottom back corner of the skirt to create a channel for the cable.

If i was you i would reorganize all of the devices, run all the cables in the same direction and as shown in another comment run them down the leg of the shelf and then across to the tv. And move the PC to the shelf. (Maybe the side of the shelf)

Professional electrician and AV tech here.

Personally, and this may be overkill, but an HDMI/video matrix would do wonders to cut down the number of cables you're working with. You'd be able to group your cables within that shelving unit, so that you can run a single HDMI to your TV. You analog consoles would need a digital converter between the console and the matrix, but since the TV itself has to do the conversation anyway and will already introduce input lag, you're up a creek there anyway. I'd cut a plug behind the TV, as well as low volt passthrough. If you're handy and can patch drywall/paint, I'd run smurf tube from that shelving unit through the wall to behind the TV. And as many others have said, velcro straps, not zipties.

If you don't want to go bananas with all that, then velcro strap everything as neatly as you can. You'd also be wise to separate power and data/video cables.

I tried this with velcro ties. Looked good for a while. Then I had to replace one and add another cable. It was a royal pain unwrapping everything and rewrapping it.

Haven't used them, but look interesting:

Lots of good ideas here. This is my take:

Get a bunch of Velcro cable ties. Start grouping things together. As you go, you're going to get better placement ideas. Once everything is organized, you can decide the next step. Personally, I would look at having the PC in the bookshelf, and look for a way to put the cables in the wall.

If you do that, I'd suggest having 2 cable runs with a string looping through so that when you change things up you can easily pull a new cable.

Longer cables so you can wrap the slack and hide it?

Here's my idea: manage the cables.

You don't need ideas, you just need to start.

Good lord it’s like the physical embodiment of one of your comments

I can’t get the cables looking good

It's because you plan and do cables in the early stages, not in the end stage, if you ever want it to look good.

The only thing I can think of now:

Powerful golden spray paint on all cables. Make it shine, make it look like it was all intended like this.

I would say at this point any type of management would be good lol

Looks fine to me.

Some of the cables need to be longer to not have that effect where they're being pulled against their own weight.

Then, lean into it: https://www.instructables.com/Maximum-Wire-Management/

You can buy these cable runs too (for example). Hide cables by running them along the base of your walls. Just match the color with your walls so it doesn’t stand out so much.

Move the pc next to the shelf.

Move the sub under the tv.

Get surface mount cable runs and go down from the tv to the floor, over to the shelf, and up along the side of the shelf.

You could look into getting some cable channels as a pretty cheap and easy solution. They're just plastic half-tubes that you can bundle the cables into and stick to the wall, so you could just have one pipe that runs up the wall to the back of the TV. You can paint them to match the wall and hide it a bit, too.

Wire ties. Literally just zip ties. Keeps them easy to get to but looks cool as fuck if you bundle them like a wiring harness.

Not sure if it's an option for you but, make a cabinet hidey-hole thing on the other side of the wall, run cables through wall and plug in somewhere over there, profit. That is, hide the mess somewhere else.

Swap the red LEDs for blue, should tie the whole room together.

The wall plate is a great idea if you don't mind cutting holes in the wall.

Honestly, I'd grab a couple of acoustic tiles to put on either side of the TV and chuck all that shit behind them. Maybe cinch up and ziptie anything I know doesn't need to move for a while.

Entertainment stand/cabinet thing under the TV.

You could be artsy about it and attach the cables to the wall in straight runs with 90s, but the execution of that is harder.

Assuming you can cut into the wall… This is likely the cleanest option without doing electrical work.

https://www.homedepot.com/p/Commercial-Electric-Flat-Panel-TV-Cable-Organizer-Kit-5623-WH/305090874

If that extension cable jump isn’t up to the electric code they do make something similar where you can tie it into the hardwire as well. It doesn’t look like you have an outlet in the same stud section though. Which would make that harder.

Any remaining cables horizontally I’d just stuff in something like this above the trim at the bottom. You’d probably want to either source a black one or just paint it to match your walls.

https://www.homedepot.com/p/Commercial-Electric-4-ft-Flat-Screen-TV-Cord-Cover-A31-KW/304502793