Again, "dumb" is not a great word to use here. Up until recently there were not realistic alternatives that would provide any kind of decent yield for many crops.

Yes, with modern tilling machinery there are now alternatives available in some situations (min-till, disc only etc) which can avoid some of the potential ill effects of tilling.

The type of intensive and regular tilling currently practiced in industrialized agriculture is part of a system that relies on the cheap availability of chemical fertilizers and pest control, which in turn were supported by the political and social developments at the time. Research and development of alternative farming systems were almost abandoned for decades and crops that took advantage of the chemical fertilization/tilling approach were prioritized to the point that we now essentially farm only a handful of different crop strains. Within this system, you are correct, no alternatives existed. But that doesn't mean that it made a lot of sense and that there weren't plenty of early warning signs that other approaches should be explored.