This is what I mean. Most of the fights are really obvious what you need to do, so you do it. Not interesting. It's like when you fight a Zelda boss and they have a glowing eye and you're like "gee wonder if I need to hit that 3 times". They kinda drag on a bit too. The secret truth of Metroid is that there's never really been any truly great Metroid boss fights (good at best) so this is not entirely surprising to me.
Honestly though the biggest offenders are the EMMI sections, which are crimes. I don't know how you can play this and not think they completely destroy the pacing. The game railroads you into a direction, and you enter a zone and have no idea where to go, and exploration slows to a crawl as you wait for Cyber Dog to get bored with an area and leave. You have an anti-dog button that's tied to a meter, so when Cyber Dog leaves the room and then arbitrarily decides to turn around and come back a few seconds later, you're screwed. You can run, which means you might get cornered and have to restart (having wasted a bunch of time and accomplished nothing) or you can evade it which is not satisfying because you still have to deal with this piece of shit one way or the other. There were a few times where the EMMI kept cornering me and I had to restart, only to find out that the direction I was trying to go was a dead end. I can tell you I did not feel good when that was happening! You can try sprinting through each area too, but then Cyber Dog keys in on you immediately. I've had equal success/lack of success by being stealthy or speedy, and both feel bad and are irritating.
Maybe the most impressive part of it all is the instant death scene; you can counter it, and the counter SOMEHOW feels both super loose AND super strict. I don't know how they managed it! It's like a small frame window, that you need to preempt because of input delay, but not too much? Or something? I dunno, it sucks. It all sucks. EMMIs suck and completely ruin the game. If it was just mediocre or even bad boss fights, and the stupid melee counter, I would like it enough to still like the game overall. But the EMMIs...
Just...why...