I don't think Stotts could have replaced Mark Jackson and turned the Warriors from a solid playoff team to a 67 win juggernaut and champion. No one thought the Warriors were amazingly talented or a sleeping giant or any such thing when Kerr took over. I remember that offseason, in a thread here I picked them to be an approximately 50-win 3 seed and people found that to be too high. Kerr proved himself to be an excellent coach, building a great scheme that took full advantage of the players he had--Draymond Green potentially never breaks out as a star under a less creative coach.
Stotts is probably an average coach overall. I don't think he's terrible, but he's one of the many coaches that generally is very replaceable--doesn't really help the team get to another level (but also doesn't make them worse than their talent). Talent is always paramount, but coaching is important to maximize talent. I'd much rather have Kerr as coach than Stotts.