Your first sentence is complaining about our C's getting dragged away from the paint. That is modern basketball and has nothing to do with Casey. Outside of the times you play Denver and Philly, a C wont be playing in the paint much. That is why I assumed you were complaining about new basketball.
And Golden State has won 4 titles running the exact defense Casey runs. OK they don't switch 100% of the time, but they also don't run out a bunch of rookies and young players. Almost all younger teams will switch everything since it is so much easier.
His offense is bad. His ATO plays are brutal. How do you run an inbounds play at the end of a game and not set a single screen? Basically all of this exact stuff was said about him in Toronto. He had Siakim, VanVleet, and OG as young players and they all turned out fine, and probably above where most figured they would end up. I see that path here as well. Casey builds the foundation and then another coach comes in to finish the job. Install more complicated defenses/offenses and build off the foundation Casey built.
But if they fired him today I wouldn't be upset. Especially if it was to bring in someone like Atkins.