Swedrami: - the melee takedowns REALLY need to be nerfed somehow (have it on a cooldown AND/OR opponents need to be stunned/incapacitated first AND/OR have other nearby opponents not just stand there politely and watch along during the takedown animation, etc)
This is a problem in most games that have special takedowns. The only one I've seen so far that actually lets enemies behave normally, still attack you, hit you and even kill you while doing them was in Warhammer 40K: Space Marine. You use the takedowns to regain health, but if you do them at a bad time, they are an instant death sentence. Complete invulnerability should NEVER be a thing. You should have to think about when to use them, not use them as an invulnerability window and spam them non-stop...
And yeah, allowing them to be done whenever/on a full health enemy is also beyond stupid. "Will I go into a gunfight with that enemy or will I just approach them and press E to instantly kill them while being completely invulnerable.... Decisions, decisions....". The game ceases to be an FPS, but devolves into "Close the distance and press button."
IMO, these finishing attacks should never be a central part of any FPS and should rarely take precedence over just shooting the enemy dead (one of the major reasons I dislike the new Dooms since it's so heavily ingrained into the core gameplay loop). Or tying health or resource recovery to them for example.