The Marauder in Doom Eternal & Rufus in Remake fundamentally have the same issue for players – they're antithetical to the lessons and gameplay strategy skills that the rest of the game is reinforcing and establishing. It's not just that you have to "git gud" to beat them (you can), but they're discordant with the rest of the growth and progression of the player-informed combat in a way that's frequently less fun to people who enjoy everything else about the game, rather than being a challenge to the people who love everything else about the game. It's why if there were a Souls boss who had an un-dodgable & unblockable AoE move that forced you to beat him quickly, it would be disliked because it's antithetical to the design and skill progression for that game.
It's really a matter of how "sharp" those encounters are when compared against the rest of the game's more dynamically approachable combat solutions that does this. While Mr. X in Resident Evil 2 Remake is stressful as hell, he's just a better version of the other zombies. He's more proactive, and much harder to stop – but the skills that you use to stop him are essentially the same as how you deal with other zombies. He just forces you to rely on evasion and escape, and only use combat when necessary. This also pushes against the player conserving ammunition vs. not allowing zombies to congregate in hordes. He is very much a culmination of the skills that the game trains you for, rather than being antithetical to those skills.
None of those things are necessarily bad, even though they're all difficult & probably stressful to deal with. They have to be looked at in context with everything else leading up to, and growing off of them, and then should be adjusted in order to fit within that path – and there are a ton of ways to tackle that, very few of which are usually simple solutions about the boss or something, depending on how much it spiders out into the rest of the gameplay systems around it, and how those need to react to & with it as well.