Syndra's ult has counterplay.
,
, and (to avoid it) 
Cass has the counterplay of outrange, burst, or out-dps her. If you want to tank her, that's like wanting to be able to tank the adc.
Even Kass's ult has some counterplay. He's extremely reliant on it to both avoid damage and get in range to put out his own damage. If you save your cc until it's on cooldown, you can hit him with that when he can't avoid it.
There are also non-squishy champions that lack counterplay. What's the counterplay to Malphite's ult? You can't cc him during it, so do you Flash it? Yeah those cooldowns are comparable.
Same thing with Olaf. The only way to get away from him is have enough of your own mobility to get away from him or be able to kill him faster than he can kill you.
Vi ult? You can't even run away from that. Literally the only real counterplay to that is
, and even then she has plenty of time to set up a Q for when you pop back out.
FYI, I don't hate any of these champions. The only one i've played a significant number of games on is Malphite. None of those mages are among my preferred picks. Counterplay is a good thing to have, but it isn't always there. This is true of both squishies and tanks alike.