I don't think that I agree on this point. I mean, Grounded is probably the worst Superman story ever, but IMHO it didn't ruin Superman's reputation beyond repair. It was just an extremely bad storyline, but every character sooner or later is involved in a bad storyline, and even if this happened with Superman more often than not in the latest 20 years, it's not like they made Superman a murderer or something like that.
By the way, maybe it is true that most people recognize Superman because of some silly elements of the 50s (multi-colored kryptonite) or the 70s (Reeve), but all of these elements had been entirely re-introduced way before the New52. I didn't read Lois and Clark regularly, so I don't really know which version of the characters was used there, but from a strictly technical point of view pre-FP Superman ISN'T Byrne Superman, but rather Byrne Superman mixed with Waid Superman (Birthright) and Johns Superman (Secret Origins).
Frankly speaking, I think that the only reason they made Superman so strongly involved in FP was because they wanted to get rid of the marriage - which, more or less, was the ONLY thing which couldn't be erased with the umpteenth soft retcon.