Nostalgia is a powerful thing and 7 is old enough for a newer generation to see it without being blinded by it. It's just not that great of a game, i.e. the materia system makes all the character really samey, the game loves shoving really bad minigames at you way too much, etc.
'Nostalgia is the only reason anyone ever liked FF7' is such a lazy argument, and is pretty much at the heart of the gaming-hipsters anti-ff7 sentiment.
After all, when the game came out and was consistently rated amongst the best games ever, there was no nostalgia then. Similarly OOT which has its own share of problems is still consistently rated highly even though apparently the newer generation should see it for what it is without being blinded by nostalgia.
The truth is SE screwed the Final Fantasy brand, and FF7 was the victim. If SE had been consistently producing games that people could love then it would be higher rated. As it is we essentially had a generation and a half where people were saying "Final Fantasy is shit" and they were right,