I think a big part of the problem is the time investment and the fact most people really vibe with only a few types of games.
On time investment: in order to say anything interesting about the game, anything you couldn't get from watching someone play it for two minutes, you'd need someone to take the time to finish it, often 50+ hours, and probably more to digest it and to play stuff around the sides (achievements, collecting. Given an 8 hour work day, and reasonable breaks, that's easily a week or more of just playing before you start writing. Then you've got to write with better insight into mechanics, design etc than the average guy, which a lot of critics fail at. Not just what mechanically does the game do, but clearheadedly why is that different, what makes that good and bad, how do they reinforce or work against the games themes.
On subjectivity: I could not review a first person shooter. I could not review an RPG like Skyrim. It's not because I couldn't play those games, or even derive some enjoyment. But rather that I know my mind, and I know that I have a strategic optimizing mind that left alone would rather play spreadsheet simulator stuff like rule the waves or dwarf fortress or football manager. Complexity is my god. But that's not the route to good design for most people. Similarly, guy who only plays CSGO probably shouldn't be reviewing disco Elysium.
All of this put together means an ideal reviewer would be working on a narrow selection of games, taking weeks or more for each one. And they'd be competing with people making excellent video essays for free on YouTube or whatever. Text is already a niche (hence declining film/book reviews also)