Flippanarchy

Britain's next election...

The UK electoral system may as well be from Mars when compared to the USA.

• For one, they have 650 MPs representing a population of 67 million. The US has 535 total reps split across a bicameral legislature. Combining Texas + California, you have 90 house seats and 4 senators representing 70 million people! It's incredibly important for all of those people to be on the same page when such high leverage seats are on the line.
• The byzantine system of the Senate and the Electoral College similarly fuck with election strategy. It doesn't mean jack shit if your progressive candidates draw 30 million extra votes if those votes come from California and NY.
• A motion can dissolve the UK government and trigger a new vote at any time, the US can't do shit until the next election cycle.

Keep running down the list and it becomes more and more obvious that US elections have extremely high stakes, keeping the establishment parties nice and comfy.

Remember, the Republican Party started as a third party...

It emerged at a time when both major parties were losing ground with their voter base, not spontaneously from one side of the political spectrum. In 1854, 5 new parties were vying for seats which gave them lots of room to maneuver. [They had even more room than today when you compare 1800s representation against the 435 rep cap we have now.]

Today there's no MAGA splinter party; the GOP is in a firm lockstep and polls indicate that their core base will never waiver. Unless you can totally supplant the Dems on the left in one fell swoop, you're still stuck at their negotiating table. You might get a new party logo on your name tag but you're as much at the whims of fascist collaborators as before.

[MAGA did] not fundamentally challenging the core beliefs of the party

This is incredibly ironic because decades of grooming went into supplanting the old 20th century GOP platform. It feels like nothing changed but that's due to how persistent and focused the campaign was. Look at John McCain. One of the last true, piece of shit, old school Republicans and he ended his long established career blocking MAGA.

reforming the Dems would require fundamentally uprooting their core values and power structure

The lack of core values has been a criticism for decades, they're a blank slate in that department. Would it be a more drastic heel turn than shifting the "party of small government and tax cuts" into "record breaking debt, spending and raising taxes"?

Donors and DNC power structures only matter as tools of suppression. If you can break the seal and get the votes in spite of those roadblocks, you can keep the votes without them.

old financial backers and supporters of centrist policies will walk away

If the campaign money shifts away from a newly progressive Democrat party, where will it go to? A new center right party courting R votes? They've shown that strategy doesn't work. A new spineless, controlled "leftist" opposition party? Well then they're stuck building against all the two party roadblocks they put up themselves!