With alot of the CC gone, the counters are limited, which is why dive heroes such as Genji are dominating right now.
Things such as turrets, Sombra hack, McCree homing grenade are kind of soft counters. You can also play Bastion using turret mode which is relativley forgiving on the aim side of things. Or you can play tanks such as Rein who doesnt really need to aim. You dont counter hyper mobiity with that, but they dont do much to you in return. If Genji blades, you do have shatter though.
Also people who say aim counters mobility is nonsense. The better the mobility, the higher the bar is set of how good your aim needs to be to be able to hit your target. That means mobility is the counter to aim not the other way around. And even if your aim is good enough, youre just set on even grounds, it doesnt put you into an advantage situation.