The API is not gone, and is still free for both “for non-commercial researchers and academics under our published usage threshold” and “for moderator tools and bots”
https://www.redditinc.com/blog/apifacts
There are several ways to add your personal API key to (modified) final versions of Sync, Relay, Infinity, and even Apollo on iOS to be able to continue to use those clients, however Reddit has changed how Reddit links work, so those methods are becoming more and more broken.
As a counter-anecdote, I’ve had 30mg generics from Sun and Mylan, and both have been the same or better than the name brand Vyvanse.
Not discounting your experience, I’m sure there are differences in the formulation that probably affect some people and not others.