ZM is one of the Nintendo games that most respects the player intuition and curiosity since... Super Metroid. The fact that they purposefuly included speedrunning tricks, secret paths and such is very exciting to me and makes me very sad that the Sakamoto games since (M:OM, Samus Returns) being much more safe in that regard. Heck, Samus Returns seemed so afraid of crafting shinespark puzzles that they outright gave a slowing time power up instead lol. I'm not saying they were actually afraid, it could be due to the 3DS fps tanking if Samus used a Speed Booster, but it feels that way.
Fusion is good but people overrate the horror elements too much. Yes the first time you're actually forced to face and run from SA-X feels a bit scary and the elevator stopping is genius, but those only work once. Which seems to me little worth of so much praise in a series like Metroid that depends so much on being replayable. Again, it's a good game.
My dream 2D Metroid would have the scope and world design of Super, the analog aim and lock of Samus Returns, and the controls and physics of ZM (them ballspark puzzles, dayum). And maybe Fusion bosses. Metroid bosses in general kinda suck imo.