I'm too scatter brain to really give this question justice but it's a combination of things.

On the one hand you have the die hard fans (read: addicts) that enable such behaviour with yearly purchases of the CoDs, NBAs, Fifas etc. On the other hand you have the fans that don't necessarily buy into those annual reskins but nonetheless support practices like Day 1 DLC, Microtransactions, Loot boxes, Pay2Win, Battlepasses etc on top of the "base" game. (How much does it cost to buy the latest Assassins Creed in full?)

That's in terms of monetization. When it comes to gameplay what's easiest to create hype advertising around? Graphics, the open world dick measuring content and the how many hours of value (read: grind) circle jerk. Call it a preview or a service and promise to make it better down the line if none of the above has worked out. Rinse and repeat. The biggest example of this is Ubisoft, can hardly tell their games apart. Compare to this to the Ubisoft of a decade ago. Never mind how most games now try to appeal to everybody instead of owning a niche.

But then there's the issue of people sometimes just not really being interested in pushing the envelope. Look at how controversial/mixed the reception for Death Stranding was. I personaly loved Deathloop, a lot of people thought it was BS how it's just the same 4 areas but to me that IS the appeal. It would have been safer for them to just make a reskinned dishonored with flipped assets in a bigger world or some kind of forced rpg grind and people might have thought that was innovative instead of what they actually tried to do. It's because sometimes people do emphasize quantity over quality. And some games do suffer if they don't have some kind of "streamer" appeal to it as people really like watching/hosting play-throughs but that's another phenomena all together.