I mean it’s really no big achievement to complete the art museum since all you’re doing is pretty much waiting for Redd to show up and hope that he has the one you need as compared to the fish and bug collections wherein you have to work to get them. So yeah, it’s still just as impressive as it takes a lot of patience and perseverance to farm them since you eventually start getting a lot of duplicates towards the end.
I think completing any wing of the museum is a pretty big achievement. Probably one of the bigger motivations of the game.
I guess one of the reasons that I don't want to TT is that it burns through content that's supposed to last a long-time (paying off loans, finishing the museum, etc.) in a matter of days or even hours. That's not really how I want to play, especially since I usually play in 30 minute segments once or twice a day at most.