I think there are more than a few factors here but it mostly has to do with the natural loss of talent game studios have endured over the last decade.
Arkham series had 3 games on the same engine that were able to have multiple iterations of each title allowing the codebase and talent to grow naturally with the games. It's been 8 years since Arkham Knight. If I recall that game was poorly received at launch. Though it's made a lot of money, it didn't make as much as it should have. After that I can imagine the entire team getting a shake up at rock steady.
The first Arkham game came out in 2009, with the way that layoffs and churn works in the game industry, I can't imagine many people left from the original series being left on this new title. Who is going to make the same Batman game for nearly a decade and a half?
The effect of the inevitable loss of talented individuals was something the game industry was forecasting 10+ years ago. I really think this is what we're dealing with more so across the board.
I'm going to skip this game. Maybe I'll play something simple like Momodora or go touch grass.