Here's an idea to combat mobility creep.

Implement more silences.

Seriously. Silences are the single best mechanism for dealing with highly mobile champions, since they shut down their mobility, and they can be allowed to both last longer than stuns and be easier to land since they're inherently less punishing than an actual stun.

Look at the list of champions with silences, and how short they are.

0.5 seconds. up to 2 seconds. 1.25 seconds. 1.5 seconds. up to 2 seconds. up to 1.5 seconds (when it works).

I completely understand removing silences from assassins.

were just utter cancer because of it.

That said... I wouldn't mind seeing an initiator or support released in 2018 with some silences thrown in, or even just increased duration on things like Blitz Silence.