I think when Lucas got it wrong is when he tried to make the prequels more "kids friendly" and "funny". The original trilogy was not funny, it was a dark story (although that has also been changing over the years from release to release).
Agreed 110%. They added too many burps, and farts, and other plain nonsense to cater to young kids, instead of just making it a serious film to begin with a touch of humor here and there. I know, today's generation isn't into Han's dry humor, or other witty dialog, but when they added the bumbling idiot Jar Jar, it was a mess.
