That's not how things work at all. Elite assistant coaches bring so much more to the program than you think. They do what they are told in terms of assignments given to them by Cal, but their expertise and most importantly personalities are individual traits. Payne could speak to the players on a level Cal couldn't because Payne was an elite player, who made it to the NBA from the perspective that nobody else on the staff had. He also was a guy who was willing to work with them and listen to them when they were homesick, frustrated, etc...or just wanted to put in work. Saying the program will be fine without him is one thing, but to diminish his impact is wrong.
Payne was the good cop, to Cal's hard ass, and he was the guy who had Cal's respect that if certain things needed to be said to Cal, players and other coaches often went to him/through him.
Recruiting wise, the thing about having elite staff is when you have 2 to 3 coaches who are relentless, connected, can close guys, and all the Head Coach has to do is show up on in-home and things are done....you get the level of success UK had from 2011-2015. The results speak for itself. UK rarely missed on top targets, and the staff was connected in how they viewed players but also could develop. Eye for talent/fit in the program. That's changed a bit and we've seen program still succeed, but not quite get to the level when staff was filled with the killers that I and some other fans would prefer. Doesn't mean you can't be successful but it's seemed like UK has been 1 to 2 players short ('17/'19) or just made bad choices ('16 and '18 specifically the Slice debacle, Quade Green) and this past year we'll never know how it would've ended up but my take was they weren't quite good enough to get to a Final Four/and didn't see SEC as strong as it will be this year or has been in recent years. Maybe I'd have been wrong but all we've got is opinions because unfortunately we'll never know.