It's also about doing things reliably. The only thing Cho'Gath can do reliably is be tanky.
His knockup is extremely telegraphed, by both the targeting circle on the ground, and the signature animation. It's actually impossible to not avoid if you aren't already CC'd by anything; there's always a way you can run out of it before it actually lands.
Also, if he opts for an AP build, he will have [unreliable] poke, but will not be tanky. If he opts for a tanky build, he won't have poke.
His ult one shots with True Damage, but it can only do that under extremely specific circumstances AND has an extremely short range.
Long story short - git gud. Avoid the skillshots and don't let him walk up to you, and he's not nearly as powerful.