Manifest v3 extensions work in Firefox, too. Its just the new thing. Its way easier to build cross-browser extensions with, too. V3 is actually a good thing overall, as its led to a lot of extensions being available for Firefox when the devs might have just targeted chrome. Way more feature parity between browsers with v3.

Chrome dropping support for v2 doesn't merit a response from Firefox because nothing changes for Firefox users and they're not going to drop support. Any one who actually cares (and they should) will move to Firefox on their own, so why waste advertising money on that? Eventually Firefox and any other browsers who want to allow stuff like ublock will probably have a way to do the same tasks in v3 (and the Firefox Dev team has said as much in blog posts for ages), then it'll just be a feature that doesn't work in chrome. V3 just simply doesn't have the API that ublock uses in v2.

There have been discussions for years in the w3c standards group about this whole shitshow and this is one the chrome team have basically refused to budge on despite all the other browser teams. Its honestlu a mirscle they delayed it as long as they have. This was originally supposed to happen at the start of 2023.

Chrome is kinda like a country with a overrule veto vote at the UN when it comes to w3c working groups since they can just do whatever they want anyway, and nothing will change until they no longer have that power. That said, browser feature parity is at an all time high recently and its because all the browser teams are working together better than ever. There are just these hard limits chrome chooses to stick to.