Then Assassins should be allowed to do meaningful damage to tanks, and have faster burst against ADCs.
Before you drop a 'Tanks counter Assassins'
Yes, but that should be by locking them down so their _team_ can kill them, being a meatshield that blocks their crucial skillshot from hitting the ADC, or blocking them out from the fight by zoning. Not by straight up killing them with Perma CC. The only class that should be able to achieve that are Bruisers.
And if Tanks are allowed to OS Assassins, then things like pre-nerf Rengar and Silence Talon should still exist to instantly erase ADCs. Why is one class hard-countered by their weakness when they don't even hard-counter their strength?
Personally, I think Class Strength/weaknesses need to come back in a meaningful (but still balanced) way, instead of the current meta where ADCs and Tanks have become more generalist, and as a result are forcing Bruisers and Assassins to the side.