I know what kind of games I enjoy (horror, fps, tps, action/adventure, realistic/walking sims, etc)
so if I see a new game come out in a series I like, such as COD Vanguard, I know I'm going to have fun playing it regardless of what people say on internet forums or reddit or wherever. A new COD will always be more or less what I'm familiar with so I can't really go wrong unless the devs completely flopped.
if it's a more niche game that looks kind of cool based on trailers or gameplay ive seen on youtube, I might do a "is X game worth playing" google search and see what comes up. lots of games look really cool on the surface but end up actually being a buggy disaster that is not your worth your money. Or weak combat, stupid story, starts off great but becomes a slog halfway through, etc.
Some games are also really short like can be beat in 4 hours, so is that worth buying full price 60 bucks? IMO rarely, so reading up on those negative reviews is helpful to decide what to put my money and time towards.
some games are just dead, too, like multiplayer games, so it's good to read up on how popular a game currently is before buying it.