They did not let Alex walk, he was pretty much going to leave anyway because the money was on the table and he would be stupid not to take it. He already have a ring, no need to chase another. The clear point is that during the playoffs none of the people that left actually allowed the Lakers to win since they could not get pass Phoenix.
Those stats look nice on the macro but wins are what matter and when AD and LB were hurt, the wins were not coming. The team struggled mightily during those stretches and their shooting was terrible. Who cares about their + - on Defense if the team cannot score points. Its evident that the current roster was not doing the job so shake it up.
As for defense, I believe its more to do with the defensive scheme then the individual players. We will see if scoring more is better than losing some defensive pressure.
As for Kyle Korver, here is your answer. Looks like its him that does not want to go back probably because well, its time to retire. https://nba.nbcsports.com/2021/02/05/kyle-korver-will-you-return-to-the-nba-this-season-i-dont-know/
They had Caruso's bird rights. and he wanted to stay there. There was no "he was pretty much going to leave anyway." If they wanted to keep him, he'd still be in LA. They let him walk. The money doesn't matter because they were going to be in the luxury tax no matter what.
OK fine, dismiss stats when they aren't convenient for you. Wins are what matter, yes. Guess what? Caruso and KCP were there when LAL won it all in 2020. You know that, because as you said, Caruso already has a ring. Why you think he wouldn't want more, like most athletes, is beyond me, but whatevs. Fact is, they are battle-tested winners. What has Westbrook, Ellington, Bazemore and Monk ever won?
Like you said, the Lakers two main guys, the ones that the entire team is built around, were hampered or unavailable in the playoffs. Are you seriously telling me that it's the rest of the team's fault that they couldn't get past the #1 seed and eventual WC champions without James and Davis? And do you honestly think that the Lakers roster as currently constructed, albeit likely unfinished, would have been good enough to get it done in that same situation?
Also, if a team cannot score points, then everyone should care about DPM... because if you can't manufacture enough offense, then maybe, just maybe your defense can carry you... all the way to a ring, kind of like what happened with your 2021 NBA CHAMPION MILWAUKEE BUCKS. Or your 2020 NBA CHAMPION LOS ANGELES LAKERS (Opp PTS/G: 107.6 (4th of 30). Forgive me if that hurt your eyes.
Forgive me as well for questioning your sincerity about your thoughts on scheme vs. individual defense. You are welcome to elaborate a bit more on this one and straighten me out. There's definitely a case to be made for one over the other, but I'll allow you to make it in support of your claim.
As for Kyle Korver, you knew I was being facetious, lol. He retired because he can't stay in front of anyone on defense or do anything in basketball that contributes to winning other than hitting an occasional wide-open three. That means he's washed. Like Carmelo.