So .. longer answer here I guess.
I think Metroid is one of my favorite series around overall, but I don't think the Prime series is that great, and it's an easy explanation. There is another user here whose name I don't remember but he/she also got it IMO.
The Prime games are just slow.
Part of the fun of the 2D Metroid games is how fast you can traverse the landscape as you explore, especially as you get things like the speed booster and space jump capabilities. You can just rip through areas and Samus feels nimble and fast. That feeling is completely lost in Prime, and on top of that I would say the combat is just not that good. So what are we left with? Something that has the Metroid name, and some exploration but feels like a pale imitation of the real thing IMO. They even have to go 3rd person when going into the morph ball mode because there is just no good way to make that work in first person. That should have been one of the first clues ...
If you took Returnal and wrapped it up in a Metroid package, you have the recipe for the best 3D Metroid, easily IMO. That game is so fast, and the main character can travel leaps and bounds in seconds, but it feels amazing and combat was just perfect. I remember you could tell when an enemy was attacking behind you just based on sound, so you knew when to dodge incoming fire without even seeing it.I think Metroid in 3D would be much better off with that approach.
So overall, I'll get it. I'll check it out. But I am not expecting it to wow me, I just don't think the formula is right.