What sucks the most is that the miscalculations have all added up.
Philly overestimated the fit between Embiid and Simmons. Maybe this duo could have worked 15 years ago but not in the modern NBA
Philly underestimated how much JJ Redick's shooting benefited them because it negated Embiid/Simmons' clunky fit together
Philly underestimated the edge that Jimmy Butler's go-to scoring in the clutch gave them. With him off the team, they lacked a go-to scorer
Philly overestimated Al's abilities, thinking his presence could help them and hurt Boston, neither of which happened
Philly overestimated Tobias Harris' scoring prowess because he can only thrive as a scorer if he has more scorers who can space the floor
And as always, there will always be the infamous Fultz for Tatum trade. No elaboration needed.
The only addition that really worked out for them was Josh Richardson. He was their second-best player in this series. If Josh Richardson is your second-best player, then pretty much everything has blown up in your face.
Really, it all went wrong in 2018 when they had a stronger campaign than they anticipated. Getting the third seed and winning a playoff series convinced them that they needed to become a contender ASAP when really they had all the time in the world. They jumped the gun when they cashed in their assets and tied their cap around Harris and Horford. Now they're locked into this dysfunctional group for the foreseeable future.