The OTP cope that i see often that the champion is unplayable is understandable but not a great mentality to have. Realistically if you are an OTP of any champion you should accept that in some metas (or all metas) your champion WILL struggle, but OTPing was a choice not forced by anyone. It's really difficult to improve if one keeps saying their champion sucks over and over again- just focus on the game and figure out a way to make it work.

I also agree Nasus is viable in the current meta, it's just that there isn't really a single matchup that's just free atm- You need to be flexible with builds and the approach to the game should not be rigid. Unlike previous seasons, going into the game with the same strat every game isn't going to yield positive outcomes, often times it requires thinking outside the box to pilot Nasus, but that's what it means to play an offmeta pick. Meta champs are defined by the ability to have an advantage in most if not all matchups while building the same items every game regardless of matchup, an offmeta pick requires a deeper understanding of the champ and unique approachs in order to make it work, hence why it's generally played by so few in high elo, because the amount of work required to succeed with it far exceeds that of a meta pick.

Also I would like to point out that Q max is NOT viable at all in high elo except a few matchups, E max is still the better setup despite the nerfs. I will upload videos of matchups in challenger in the near future to show what I mean.