Their web app is fundamentally broken in half a dozen ways, and has been for years. A couple examples (not all):
If you are in the middle of typing a comment and switch to another app, when you come back, it will reload the display, losing your comment.
Video shorts load in a way that hides the video after about two seconds. Editing the URL to remove the parameters fixes this.
The layout of comments/posts often breaks, forcing me to switch to "ask for desktop version" to make one feature work, then switch back to "mobile version" to make another feature work. Neither is completely functional.
As I said, there are more. As I said, I don't even remember why I rejected their app, but at this point, if they can't make a mobile web site, why would I trust them to make an app?