The idea of changing the gym system was really interesting, but trials weren't the right answer. After all, it's pretty much the same thing. The idea wasn't bad, but they could have found another way imo.
I am not saying that gen 8 gym puzzles/challenges were better, even if some actually were, but imo Galar didn't fail to give an order and explanation about how the competitive circuit works in the region. I felt that it kinda finally it made sense for gyms to exist and the different challenges, which were different from just puzzles and battling were a nice touch. Unfortunately they were easy, Gen 9 went back to make gyms loose importance and the puzzles/challenges were even worse. Some gym leaders were a little stronger than the ones in Galar (from my experience).