Regardless of your opinion of their quality, they're pretty far from B movies. B movies were lower budget films often paired with higher budget films in the old days of theater going before the blockbuster era began in the late 70s. It's not really a description of quality because many were actual good like The Incredible Shrinking Man. They were just lower budget films put out by a studio. They still basically exist today but it's more stuff like Syfy original movies, any Troma film and James Gunn's pre-Marvel films. Some are good, some are bad, some are cheesy good or so bad that they're good. The worst of it usually ended up on MST3K, but it's mainly budget thing and the market they were aiming for. So even shit like Transformers: The Last Knight isn't a B movie, but a good movie like Slither would be.
DC movies wouldn't be either.