Summary
In the summer of 2019, Philadelphia traded for Josh Richardson because they thought he could help the 76ers become the best defense in the league, and that he would fit as a secondary playmaker next to Ben Simmons. Neither of those really came to fruition. Philadelphia was 7th in the NBA in defense in '19-'20, which is good but not near the elite level they needed to be to be a real title contender given their offensive rating. On offense, Richardson was overtasked when asked to create in pick-and-roll, and wasn't the spot-up threat around Simmons and Embiid that those two need in order for the 76ers offense to be successful.
 
Richardson was theoretically a better fit on the Mavericks in '20-'21, but struggled to make a real impact in Dallas. He missed a decent chuck of games, struggled to shoot well, and his usage was also way down playing next to Luka Doncic. He then had a forgetful '21-'22 season, despite shooting really well from outside as he didn't really fit in with the Celtics as they went through their early season struggles, and the Spurs were not the most watchable team after he was traded to San Antonio.

Richardson is a two-way wing who can guard multiple positions. He has hit 38% from three over the past two seasons, which is around his career rate. He has upped his 3-point volume in recent years, and is not just a stand-still shooter, as he can hit shots off movement or off-the-dribble.

Richardson is a better defender of guards rather than wings since he's on the lighter side for a wing. He consistently puts up good steal and block rates. He will be nearly 31 years old as a free agent in 2024, so there's a chance that age-related regression could be coming soon, as there have already been some signs.
 
Cap Considerations
Richardson has a $3.1 million player option for next season, and if he declines that option he will be an unrestricted free agent with a $2.1 million cap hold and Non-Bird Rights.

Due to the increase in the salary cap not being very high, his minimum salary for '24-'25 as a free agent is less than his player option amount, so he should opt in for financial purposes if he thinks he can only get minimum offers elsewhere. The difference is minimal enough though that opting out and signing a minimum contract elsewhere is reasonable if he no longer wants to be in Miami.

If Richardson opts for free agency, the Heat will be somewhat limited in their means of re-signing him. Since they will only have his Non-Bird Rights, the most they could offer him using the Non-Bird Exception is a contract starting at $3.6 million. If that's not enough, the Heat could use their MLE or Bi-Annual Exception (if available) to offer him more than $3.6 million.

Other teams will have multiple ways to sign Richardson as even teams without cap space could likely use any of the Non-Taxpayer MLE, Room MLE, Taxpayer MLE, or Bi-Annual Exception to sign him. Since he signed a minimum contract in 2023, teams will hope to get him at the minimum in 2024 too.