Yes, according to Gil Kane's own testimony, the fact that he "didn't really enjoy" [the GL strip] and "it was sort of boring doing it" surely must have had some effect on his actual work for the book as time went on.  The inking issue evidently bothered him quite a bit. I think there was a perceptible dropping off in his art early on (though it improved in the mid-1960s when Schwartz did let him finish more of his penciling); others might disagree though.