Quick PSA on Lalachievements numbers
I'll preface this by saying that Lalachievement numbers are cool and useful information, and you're still free to argue that certain content is too difficult or uninteresting for a large amount of the playerbase, but you cannot cite the total numbers on the website as evidence to make your point. They are extremely misleading.
I looked into this matter recently because I wanted to know what is actually being tracked, and the dev explained that the only profiles actually tracked are from a bulk import done in 2018, plus anyone whose profile has been looked up on the site at some point. That's it. If you're not aware of the site, or not actively logging your achievements there, chances are you're not in their database. I certainly wasn't (despite first playing the game in 2016).
Just to put things into perspective: As of me writing this post, Lalachievements lists a total of 2395 characters with the achievement for beating Dancing Mad Ultimate. FFlogs has 5133 clear parses logged across all jobs for that fight in the last two weeks alone. Edit: To make it even more obvious, Tomestone lists 21388 cleared characters, roughly 9 times the amount on Lalachievements.
I feel like this is pretty important context for anyone discussing these numbers, because between Chaotic, Forked Tower, the recent Ultimate and now Beastmaster, I've seen them used as supposed proof of the dire state of the game or certain bits of content several times now, based on false assumptions. Not blaming anyone here because it's really confusing, just wanted to clarify that the difference is much bigger than just a handful of private profiles.
tl;dr achievement numbers on lalachievements are only useful to compare relative achievement rarity, NOT total clear numbers for content