My oven doesn't have a touchscreen but it does have touch controls and it works perfectly, it's never disturbed by the steam from the oven even when it quite visibly condenses on the surface.
My point is that it isn't always a design failure to use touch controls, sometimes it is an implementation failure that makes them unusable.
What makes it a design failure? It seems good to me. The surface is completely flat glass and easily cleaned, there is no possibility for dirt to get into the switches or accumulate in crevices.
My point is that it isn't always a design failure to use touch controls, sometimes it is an implementation failure that makes them unusable.