Most champions who have/had a silence, also have multiple ways of sticking to you, and 9/10, kill you.
Has, or should I say, had, his ult, W, and E for immense burst and mobility.
Has a leash-based snare that's very difficult to avoid at close range, and her ult for an additional silence, snare, or dash
Can just instantly burst you down before you can react, the silence preventing you from flashing/dashing away
Has a mass AoE knockup + slow, and a true damage execute.
Execute and spin. I don't think I need to say more.
His spell rotation also includes a 2.5 second supress, with ludicrous % health damage and sustained damage from voidlings + DoT
And as you can see, all of these champions were OP at some point, with the silence being toned down or straight up removed in most cases. Those who were allowed to keep the silence saw nerfs to other parts of their kits.
There is a reason that most champions nowadays don't have stealth or silences in their kits, you know. It's ten times easier to balance stuns/snares/knockups etc.