GSP has no wrestling credentials what so ever, he was able to get away with this in a era with relatively little talent, but now without years of training, he woudent hold a candle in wrestling to Usman, Woodley, and Colby (the 3 best WW of all time).
Conor defended takedowns well in the third round against khabib, who is highly accomplished in sambo, and nullified his ground game in the first.
Chad roided to the gills was far more explosive and powerful than GSP with better wrestling credentials, yet was finished in the second by Conor, who was depleted by a weight cut.
GSP's standup is basically just striking against people who can't strike and are one dimensional. Aldo would break him down and clown him in striking, Conor took out aldo with one beautiful punch.
He was successful because he was not completely one dimensional, but against conor, who is well versed in multiple martial arts, GSP is going to sleep with a family meal (unless GSP taps before he can take the full meal).