Diablo Immortal - Stay awhile and pay on your mobile

Oh, look, who came out of hiding for a cheap jab. Well done!

So you honestly think that a review should not rate a game’s quality of art? How consistent the art style is, if it is well done, if resources are wasted (by using 2k textures for door knobs, yeah that happens), if graphical glitches happen, there are MANY important aspects here. All of that can be done objectively.
It should not rate the game’s mechanics? If they achieve their purpose, or if they just downright do not work, if they are well-balanced (if that was their goal) or is one build (in RPG terms) totally dominating? Again, all of which can be objectively analyzed.
It should not rate the audio quality? If the voice over is well done, or just read by someone without emotion? If the sound makes proper use of the channels (3D/2D positioning) or is just blared through like mono sound? If the music follows a composition or is just slapped together open-game-audio with no coherence? All of which can be told objectively.
It should not rate the game’s setting, worldbuilding and story? If it is coherent within itself, objects, cities and NPCs have a convincing reason for doing what they do and aren’t just there because they need to give you a quest? If actual thought was put into WHY something is there, or if the entire world is just a theme park with no logic to it whatsoever? If the story develops in a convincing matter or is just full of deus ex machinas? Of course, this cannot be applied to every game (for example, puzzle games), but where it can be applied, it can be rated objectively.
Then there is the tech (bugs, loading times, etc.), there is the UI, etc.

All of that is factual information, that can very well be rated. If someone liked it (or not) is, at best, important for the petty ego who wants to put his opinion out there (hey, I do/did that myself, I just won’t pretend that my opinion is valuable information, but my facts sure are) and useful only for those knowing their own bias in relation to the reviewer’s. So it isn’t fully useless for some, but nowhere near as valuable as factual information about the game’s quality.
Of course, writing a proper review requires actual knowledge about game theory, game development, art, music, etc. Not everyone can do that, or should do that. Why do you think games journalism is in such a pitiable state? Too many people doing something they are bad at…

I’ll fully admit there are things about games that can not be objectively rated. Humor, for one. You can tell a game is humorous, but humor is so subjective it is pretty much impossible to objectively rate it.
But the vast majority of what makes a game can and should be rated as objectively as you can. Nobody says you can’t say if you liked it or not in addition, but if that is the focus of all you do, what useful information did you actually put out into the world?

Opinions are mostly useless due to how subjective they are (including my own, just to make that clear), though they can be fun to discuss. Facts are never useless and therefore superior information.
Some reviews try and do a separation here, by having categories like art/audio/tech/story etc. and then something like “fun factor”, which is of course mostly useless (what does it tell me if someone I don’t know had fun with a game? Not much, that’s for sure). That’s a step in the right direction, as it at least separates facts from opinion. Of course, some just use them to say “I like they graphics, I don’t like the audio, I like the story”…