sanner I think most people will say that at least all the post-EoSD mainline games are worth playing, at least until around 17-18 and onwards which is when some people will say the quality declines a bit, I can't really say but it does strike me as perhaps indicative of less interest from ZUN in thinking deeply about the construction of the game that from that point it always seems to be a boss serving as one stage's midboss and end stage boss, no more Kisumes or Lily Whites it seems
I've not gotten that far yet, I'm stuck at an impasse from playing in order where SA is too hard and so I go in a cycle of saying "fine, I'll go back and beat it after all the others", up next is UFO which is the other game people say is the hardest and it's pretty hard for me too, and then TD isn't the easiest (though some people say that, it's not for me because I've not 1CC'd on my first try like a few others) but it does feel disjointed and plainly not very fun, so I've noticed I kind of bounce around between these three and never seem to buckle down and actually motivate myself to playing one to completion like I once did