Maybe they'll win a title this year, in which case I suppose the contract was worth it. But I find it pretty hard to believe they'll be thrilled about paying the next 3 years of his deal at an average of $27M for his age 34-36 seasons.
Next year they have salary commitments to 12 players that will take them about $8 million over the luxury tax line, and given commitments to Embiid, Simmons, Horford and Tobias, there's basically no real money left for anybody else.