2014 after the Maidan coup.

There was no such thing. Yanukovich broke his election promise regarding starting the EU association process, protests happened, snipers shooting at protesters and this law happend, which resulted in his impeachment and new elections.

Even if you consider his impeachment to be sus (the Rada played it fast and loose but has the power and had the votes) ordinary elections were held soon after, legitimising the following president (Poroshenko).

When NATO threatened to allow Ukraine to join

First off, There was never a point in time where Ukraine wasn't allowed to join in principle. Membership is generally open.

Secondly, regarding European geostrategy, NATO is irrelevant in this case as Ukraine wanted to join the EU and the EU, too, is a defensive alliance.

it was a major escalation that demanded a response from Russia.

Escalation of what? Russia's inability to re-constitute parts of its empire?

See, this is what really annoys me as a European: All these "NATO is threatening Russia" takes are incredibly Seppo-brained. Also, displaying the worst part of brainrot coming out of geostrategic Realism: They're predicated on the idea that the only states ever having any agency are the US and Russia (because "superpower") and everyone else is their pawn.

What possible reason could have countries like Estonia, Latvia, Lithuania and Poland have to join NATO? Might it have something to do with being invaded, time and time again in history, by Russia and treated as colonial subjects?

Russia has been conquering its neighbours before the US even existed. Or do you seriously think a continent-sized country comes along naturally, without conquest?

(Side note: You should look at the Soviet opinion on geostrategic Realism. They called it a fig-leaf for imperialism, which is a completely fair point -- and Russia, and anyone else using this "big player and a bunch of chesspieces without will of their own" model, is guilty of the same thing.)

but because NATO is the greater evil,

NATO is a fucking joke in this conflict. For one, the US has to be dragged kicking and screaming into doing anything. Turkey is being... Turkey. Even more, for many members it's a moderating force: If you ask Poles we should immediately put boots on the ground, march to Moscow, not worry about nukes it's more important Russia gets dismantled than us not getting glassed. That's the kind of attitude Russia has, over the centuries, imprinted in its neighbours.

On balance I'm in favour of dismantling NATO, with the caveat that without Europeans in the mix, the US might get worse. But that's a general point, "NATO good" or "NATO bad" doesn't really play into whether Russia is in the fault here. And it is: It violated the territoriality integrity of Ukraine, of borders it itself very much agreed to not so long ago.

What kind of precedent does that set, saying "Here, give up your nukes and we'll respect your borders" and then violating those very borders? When you go by "the purpose of a system is what it does" then boycotting nuclear non-proliferation seems to be what Russia is intent on doing because who is ever going to give up nukes if the result is getting invaded by a nuclear power.

Last, but not least: How can it be a bloody proxy war if Russia is participating directly. And Ukraine is fighting as a proxy for... Ukraine? Do words have meaning?