I'm Perfect was not perfect
It was nowhere near perfect. In fact, the ending incensed my family and me. When are we going to stop denying marginalized individuals a happily-ever-after, just to elicit some "feels"? The ending didn't even make sense within the context of the character and the story.
So, yes, while I celebrate the stellar work of the actors and the DS community involved, the awareness it brings, the well-intentioned efforts at inclusion of the production team, I think it was extremely lazy storytelling which resulted in a disservice to DS individuals. Because basically, what the ending communicated is that 1) the overprotective mother was right all along, and her unupdated view of health of DS individuals was vindicated and 2) DS individuals really can't be trusted with their own health.
I hope that any future project that wants to spread awareness of and do justice to the DS community does not rob them of a happy ending. There is no reason to. Not if you want to show that they live lives just like everyone else: they have agency, they can get married, and they grow old.