Have you ever noticed the difference in screen quality before? Did you ever watch a YT video on something slightly better than a cathode ray monitor and thought to yourself: "hmm, this is shit."? If so, don't cheap out on the tablet. Maybe a used iPad might even be ideal. I'm leaning Apple here because Android tablet screens tend to be worse on average and there will be fewer good ones on the resale market.
If you don't want a big TV, how about a smaller one that you can cast content to? Just as another suggestion because other folks have already suggested laptops.
As you get older, your eyes turn to shit and most of this won't matter that much. So you're right to be cautious on the spending.
I proudly watch movies on my phone. If I don't want to watch Paw Patrol or Frozen it's the only way to get some not-made-for-kids content in. And I can take it to the toilet and continue watching. And I don't mean porn, just to clarify. Sure, as the cinematic experience goes, it isn't what Christopher Nolan had in mind but shit happens. It's that or nothing.
We are just asking old questions here. The printing press, novels, and pamphlets were the end of truth! We struggled, many people died, but life moved on. Then newspapers, more death, radio, world wars. Television, photoshop, the internet - fewer deaths in between but still. And life moved on.
Every new medium brought a phase of uncertainty (and possible carnage). That's where we are right now. Every time we think "this is the worst EVER." Until the next thing comes around. We will figure out the slop tsunami as well. I think fewer people will die than during the reformation.
Some people will successfully bend truth to generated video or whatever. But in the end, most will not succeed. Because we get wiser at spotting the bullshit. Q Anon showed us the learning isn't a linear development; it follows more of a two steps forward, one step back pattern.