Mouse/trackpad cursor support, keyboard shortcuts, and robust filesystem access are required to intelligently use Photoshop. Does Adobe expect that iOS will eventually get there?
And... while there are some pretty easy UI wins Apple could make there [eg: the special handling of 'photos' in many apps makes treating them as 'just files' awkward] the iOS 11 system seems reasonable for most common workflows. Do you have any specific complaints?
I'm sure adobe would like the ecosystem to get better for them over time, but there's nothing blocking their software from being useful on the iPads of today.