Being a remake of Metroid II, it's hard to review this game without comparing it back to the original, as well as Nintendo's own official remake, Samus Returns. Despite all the new additions in the realm of bosses and upgrades (all of which are a ton of fun, and really show just how much passion went into this game rather than being a simple recreation of the original with better controls and graphics), it ends up feeling like a more faithful remake than Samus Returns. Areas are all wonderfully reimagined to be some important place in Chozo civilization besides just a bunch of temples, but the layout of everything is so much more familiar coming from the original than Samus Returns ever was, along with enemy designs that are a lot more faithful to the art in the original's manual.
Like Samus Returns though, I think the game is ultimately unable to capture the heart of Metroid II. The original was practically a horror game, and so much of what gave it its feeling of dread was streamlined away. You now zip through cramped corridors too fast to feel claustrophobic and can see far enough ahead to always know what's coming up. Replenishing health and missiles at each save station and Metroids dropping a butt ton of both when killed removes any possibility of trepidation as you cautiously move forward at low health, hoping no Metroids get the drop on you. I only ran away from a Metroid encounter once, and only died once (which was during the final boss fight). The penultimate area in the game, the Metroid Nest, is a good way to sum up how I felt about this. In the original, I anxiously crept around, knowing I had to seek out the last few Metroids and kill them in order to progress, but also knowing the battering I got from each one would add up, and I ended up feeling on the brink of death throughout the entire area. In AM2R however, each Omega Metroid can be taken down quickly and easily once you get used to fighting them (which you should after just one encounter) by spamming some Super Missiles, and when each one is killed, they drop enough energy to refill whatever you lost and enough missiles to ensure you're prepared for the next fight. Instead of having any feeling of dread whatsoever, I just blasted through the area super quickly. I understand that Omega Metroids were nerfed in a patch because people complained of them being too difficult, but... maybe they went a little too far? I dunno, it just felt anticlimactic with how easy they were.
I also acknowledge that pretty much all of the decisions made that detract from the atmosphere of the original were good design decisions. The snappiness of the controls makes it a lot more fun to play (even if I never could set my controller dead zones in a way so that it wouldn't feel a little unruly), the combination of save and recharge stations is convenient and prevents any backtracking to refill resources, and even the removal of charming little details like the ability to pick which beam you wanted to use does ultimately streamline things. The swapping of the original's random unsettling noises with Prime-style music remixes that sound almost jazzy might remove the original's atmosphere, but it certainly is nicer to listen to. The lore scans might've removed some of the mystery of the original, but I liked reading about the game's areas and miscellaneous other things a lot (I'm a sucker for that kind of stuff, the kind of person who scans everything in Metroid Prime and reads every log in Pikmin games), and it definitely provided for an amazing atmosphere in the game's final area (the Metroid Lab), with the surprising twist to the final boss acting as a great way to top it off. I'd have to replay the game to see how much upgrade optionality is preserved, but I have fairly high hopes for that, and miscellaneous little additions like the built-in randomizer I could see giving the game a lot more replayability. In the end, AM2R has plenty to like, but if you do like it, it's not going to be for the same reasons you'd like Metroid II (though it does seem to understand the spirit of the game a bit more than Samus Returns). Metroid II was a horror game; Samus Returns remade it into an action game, and AM2R remade it into an adventure game.