God I wish chrome didn't remove manifest v2 
Here is the list of things that piss me off about firefox:
- It is dogshit slow
- It eats up a ludicrous amounts of RAM, which I wasn't expecting since it's one of the main things people make fun of chrome for
- It crashes constantly
- It tries to push it's "AI" bullshit on me despite me turning it off on multiple occasions
- It puts ads on my home page
- It needs to be relaunched regularly because at some point it becomes too laggy to use. It even stops loading pages altogether
- "Restore previous session" feature doesn't work half the time so restarting the browser is absolutely terrifying
- Profile management is a mess
Are there any alternatives? Is Brave any good?
The RAM thing (and it getting slow over time) is due to the default way it handles inactive tabs. Mozilla decided that users would probably prefer to have tabs be fast when switching between them, so they are kept "active" in RAM for basically ever. This was not the case back when RAM was considered a scarce resource.
I installed an extension to automatically unload tabs after a certain period of inactivity and RAM usage is no longer a problem. As of the most recent update you can also unload tabs manually natively.
As for the ads, AI, etc, all of that can be turned off, and generally only has to be turned off once. Though you may want to look into a fork that does this for you, like LibreWolf.
Which addon is this? Search engines are unfortunately useless these days, and I just got a thousand auto generated articles about how Firefox has an unload tabs context menu button now.
https://addons.mozilla.org/en-US/firefox/addon/auto-tab-discard/
highly recommend you install this @kleeon@hexbear.net . Its a huge memory saver.
What OS are you on and what other addons are you using? Something definitely odd seems to be going on with your install.