The problem with NTR is that it can be used in such a broad way in that I may know a story that had both vanilla and NTR tags. It was very much a vanilla story.
Main girl likes main boy but is shy and when she as gotten the courage to confess to him she finds girl #2 confessing so main girl is in tears. Some days pass and main girls finds girl #2 getting boned by a different boy. Main girl and main boys are at a bus stop alone and talking happens, girl #2 wasn't true to him and then main girl confess in very cute/vanilla way and boy gives a vanilla response then fucking begins.

Point being that if a saw the NTR and not just the vanilla tag I would of ignored a good/decent vanilla. Still if people see the NTR tag they are going to be like this:

NTR, short for Netorare, involves one lover being stolen away from their lover by a 3rd party with their former lover often finding out in a very cruel way. Commonly paired with rape, mind break, and cheating.