While it's true we all wish this kind of episode to be the norm instead of an exception, it's weird to me how some people seem to be complaining about this episode being too good. Like it's not important enough to deserve this level of care and animation.
This is just as important as any of Goh's Project Mew and Ash's PWC episodes. It's not filler just because it's not related to one of the only two plot points JN has. It ties to a previous series plot point, a previous MC's goal, it closes an entire storyline.
I get the feeling some complain about them choosing to spend resources to make this episode better than average just because "they didn't spend them where I wanted them to". Well, I'm sure their resources are limited, so they can't please everyone. This episode's plot has been in the making since SM ended, whereas the other character returns were most likely done with much shorter time frames. It's only natural an episode like this would get a bit more attention.
I agree animation for Ash's battles has been underwhelming, with a few exceptions. But, if anything, this episode looking as good as it did and having above average writing gave me hope that they can deliver higher quality episodes for Journey's climax, including better animation for Ash's final battles. I'm not naive enough to expect it to change drastically, but after this episode I'd be surprised if the quality didn't match this episode's for this series climax moments.
I feel that's better than being bitter that it didn't happen before, in whatever episode your favorite character was in.