I do not immediately see how to maximize value in the player development lab. For me, that is exciting! I'm glad to tinker around with it and get it to serve my needs.
My impression is that (like many of the OOTP game systems) there is no 100% "correct" way to use the PDL. We all certainly have different styles and viewpoints in how we construct rosters and utilize players of different skillsets. Each of us decides how these tools best serve the goals for our sim in that moment. Finding the "optimal" solution, by having someone explain it to me in a YouTube video or in a post doesn't really line up with how I have fun in this game.
However, I acknowledge that others do have a desire to min/max or find the "best" way to use tools in the game. That is totally valid! This game has so many options, and ways to enjoy it. It's a big reason why I've become an instant fan of the game!