I agree with you up to one point, traditional Centers and Power forwards have had the longest careers in the league. The problem is their games are no longer sexy or appealing to the average fan, not the hardcore fan.
If you look at Nurkic, Jonas, Nikola, Robin, Jokic, KAT, Drummond and Rudy, their games are not always sexy and cute, but they are effective.
Yes, there are some areas Jah needs to improve, but be clear, Philly don't want to let him go if they think they have another Sam Bowie or Greg Oden named Joel Embiid.