The wild grains would have been very different from today's, though, and the plants would have been too.

Yes, for most of them. Today's carrots are very different from the original crops, as an easy example. Even the predominant colour wasn't as such until a couple of centuries ago.

Far less appetizing, I'd imagine.

Can we agree that is at best very subjective to answer?

It doesn't require much effort to find everyday food items that have changed wildly in its palatability over the course of one or two generations. Not processed foods; basic food items.

There is carbon/nitrogen isotope testing that shows that our distant predecessors also subsisted off roots and tubers.

And we still do. Our ancestors got that right. Potatoes, kassava and taro are good examples of that.