Yeah, a lot of Doctor Who is crap if you think about it. Probably true of the old series, too.

Game of Thrones took a dip too; season 7 was "this is getting dumb but fun" and season 8 was "this is just dumb" for a lot of fans. There it's suspect the producers wanted to get it over with so they could go tell stories about the Confederacy instead.

Reviews suggests your low hopes for Dark Phoenix are justified.