So how I see it, off meta builds vary in viability over elos. A example of this is I'm a huge fan of a more AP heavy nami build for pretty much everything up till plat 2. Been a fan of it from before they ever added utility scaling to supports. Reason is I would rather have 1 large heal to compensate for a less talented adc, the damage boost to her QWER all make it so my carry's don't have to do as much damage to snag kills on targets, and opponents make plenty of mistakes that I can be opportunistic with. A good adc might get 4-5 autos off in a brief fight/trade but a less talented one only managed 2-3 when they make mistakes like canceling the animation early or don't dodge ability's that are easily sidestepped so a build fully dedicated to enhancing them ends up being less effective the worse they play. This playstyle of mine eventually becomes harder to thrive with once folks are not giving you the same windows to play around or don't misplay their responses. That being said, something like what 95% of the ladder its viable so who really cares?
Tldr, if your winning 55%+ people might want to consider that off meta build match your playstyle better.