I have seen blocked field goals and extra points. I even saw a fake FG or extra point on one of my teams their current season. Don't know for sure if it was a fake, or the snap was fumbled and the holder just tried to run with it.
On returns though, if the KO team is converging too fast, that is more than made up for by the lack of vision in the return men to bounce it outside to gain ridiculous amounts of yardage. It may not be the best for realism, but it works for me. Personally, I haven't seen what I would call an inordinate amount of returns for TDs.