It's no different to people claiming that the market is "flooded" with FPS games (singleplayer FPS games have always been relatively rare and they have grown even rarer in recent years). Some people think that FPS games all look and play the same. A lot of people think that, for example, something like Perfect Dark or GoldenEye is no different to Halo. This makes no sense to anyone familiar with how they actually play, but gamers love being reductive. For example, some people felt that Battlefield: Hardline was a "reskin" of Battlefield 4. Battlefield 4 was an FPS game where you basically walked down a wide corridor and shot things. Hardline was essentially a stealth game. That encouraged players to not shoot people. With frequent bouts of branching and non-linear level design.
You know this one game that is all about shooting people and this other game that is specifically about not shooting people if you can avoid it? Yea, they're totes the same.
I think that there is, however a grain of truth to the idea that a lot of Sony's games are shoehorned into a particular mold. What do I mean by this? You know how there's a new Perfect Dark coming? Well, it's very telling that some people's idea -- particularly on Era -- of the best way to bring back Perfect Dark sounds an awful lot like wanting Microsoft to make a game cynically designed to compete with Sony's games. They want it to be third person. They want it to have a stealth focus. They want it to focus on its protagonist and try to make her "iconic". They want it to focus on her life struggles, basically.
What's curious is that Sony do make first person games. But they're almost all VR games now. There is a bit of a third person fixation in sections of the current gaming market. People being vocally "disappointed" that Cyberpunk 2077 was an FPS game instead of a TPS game is an example of that. They wanted Cyberpunk 2077 to be a certain kind of game. This kind of game could be crudely distilled down to a bunch of adjectives like "third person cinematic action game with RPG elements", to be deeply reductive.
Here's what I wonder to myself sometimes: If a Sony-owned studio wanted to make System Shock 3 with a different name, would they make something like Prey (or Alien: Isolation for the PSVR audience), or would they make something like Dead Space? Would Sony nudge them to steer away from first person perspective, and gameplay with a late 90s PC mindset in favor of over the shoulder third person shooter action with a cinematic camera that never cuts? Would Sony have greenlit Horizon: Zero Dawn if it had been a Far Cry: Primal-esque first person title? Still have a great female protagonist, but you never see her face ingame because all the cutscenes are first person. Would Sony be okay with that?
If a Sony studio came to Sony and said, "We want to make a game that's basically STALKER with another name," would Sony greenlight that? Or would Sony want the game to be pushed into some kind of third person open world post-apocalyptic third person shooter with a cinematic presentation and a strongly defined protagonist mold? I guess we may never know. Most of this stuff is firmly behind closed doors.