I think the answer is to not buff fighter damage in the early parts of laning. See fighters already outscale tanks. I think the ideal world is that in the early game tanks and fighters are roughly even, and then at some point the finghter's push and damage is so high the tank can't deal, but by that point 5v5's are a thing so the tank has the opportunity to win through being a good front liner for his team cuz winning his lane is no longer an option. And then in the very late game the comp with more damage just outscales.
Honestly i'm not sure tanks need a nerf to their damage. They already have pretty low agency in the early-mid game. I will say that they find a way to nerf tank damage even further, then they should couple that with a buff to their early game tankiness. Like no, the tank is not gonna be able to beat out the fighter in lane phase, but they aren't going to die repeatedly either and they have stats to just start frontlining earlier on.
See Riot needs to stop trying to make generalists a thing. Just let there be tanks who just....are tanks. They meat shield, they don't dps. For instance I think the move to make Maokai's ult root duration longer is a really good move in the right direction, buffing W damage tho...not good. It just further increases the focus on up front burst damage, which I already mentioned is over emphasized in the current game state. I'd say a better move would be to not increase W's damage, and instead slightly increase the healing from his passive. Or maybe make his W grant an extra charge to activate his passive more often. This increases his survivability early on rather than damage, and leaves open a window for counterplay by ccing him or kiting before he can auto, or with grievous wounds.