Yeah, it was a well made movie and all that, sure, but it suffers from everything you said pretty much. They shouldn't have killed off T'Challa, they shouldn't have wasted time on Riri, and Shuri becoming Black Panther felt forced.
I haven't watched it since I first saw it, and have no intention of rewatching. It was just...a movie that happened.
Watch our "BLEACH Can't Fear Your Own World" full fandub:
https://youtu.be/a2s_RdYM_pE?si=5kHTTbvJX4CY8Zk8