Disagree on Lamar not being able to defend SFs.
Last 2 seasons opposing SFs have a 47.8% eFG% with him as their primary defender. League average eFG% for SFs this season is 53.8%, last season it was 53.2%. So over the past 2 seasons he is holding opposing SFs ~6% lower than the league average.
Defense has never been his problem. He is a solid 2 through 4 defender. His struggles come against quicker opponents. Why the overlap of him and Okoro works defensively.
And just like Okoro, we need to keep context in our minds. Lamar is still a young player at 25. He's appeared in less than 2 seasons worth of games and hasn't even cracked 2500 total minutes played at the NBA level for his career. To drive that point home, Mobley is going to play more total minutes this season than Lamar has played in his entire career.
Young, inexperienced players can improve. Lamar, like Okoro, has improved his shooting and scoring efficiencies every season. Like Okoro, his 3Pr is climbing each season. And like Okoro, his numbers over the last half of the season are climbing to levels that make them very useful rotation players in the modern NBA. Lamar has shooting splits of 51.9/36.4/82.6 over his last 30 games played. Since he re-entered the rotation on 2/23 (10 games) he is shooting 41.2% from 3 on almost 2 attempts per game. He's also been a Net +12 player on the floor over that stretch, a stretch where we have played the 2nd, 3rd, and 4th best teams in the league and a well-coached Miami team twice.
If Lamar is developing into what he has been over the last few months, he's a very useful NBA player, especially with him proving that he can bang with some legit big men in the league over the past 10 games.