A team cannot function without rim protection, can Kyrie do a better job guarding his man and fighting over screens? definitely but that's not the main issue, the main problem is that our guards are funneling the opposing players to our big man, and our big man are funneling the opposing players to the basket for easy layups.
Kyrie and the team looked pretty damn elite on defense when they had a real big man back there, and no team in the NBA can function without a rim protector, Curry is just as average as Kyrie is on defense but they have an elite defense because Donkey Green is always back there to stop anybody that blows by Curry which happens all the time.
Guards always blow by defenders in the NBA, its very hard fighting over all the screens and stay glued to your man and shut down penetration on the perimeter, if you watch most great defensive teams they don't shut down penetration because its nearly impossible to do so, but they do a great job of funneling players and never allowing easy baskets at the rim, that's the key to any good defense you can't have layups and dunks everytime a player blows by a defender, you just can't.