Well, keep in mind they can on-demand dumb fire their ults. Galio requires an ally. This means while Pantheon and Fiddlesticks are generally known not to have their ult's power factored into their laning since they're too slow to reliably use, such as a Liss or Lee Sin ult, Galio is even further put behind because he physically can't use it without an ally, much like Shen.
Galio's ult has a massive CD as well as an ally requirement. Not only that, it requires good team work to pull off since one you target an ally's position, Galio lands on that spot no matter where the champions go. It's not meant to be an ability with a high avoidance rate, most abilities aren't. Abilities are designed with the intention that they'll be hitting most of the time. Those that don't get wild effects, such as Pantheon's 1000 base damage 16 ult.
It's definitely nothing compared to a Malphite ult. Malphite's ult is sudden and usually unavoidable. The only counterplay to it really is the CD and a person actively waiting with their finger over the flash button for Malphite's model to lurch forward suddenly to hopefully flash out in time. Galio's gives time to Zhonyas, flash, prepare in any way you can, etc.
The reason the entire ring is a knock up and not just the inner portion is that he lands where he targeted. This gives time for the ally/enemy champion to move away in natural combat procedures, so the entire circle being dangerous is necessary or actually landing the middle part would be difficult without CC from another champion, already gimping a reliance-based ability.
