If this will be future of software in 20 years nobody will understand what the hell software actually does. If nobody will things will get to implode quickly.
I think we'll be fine.
This feels more like Y2K panic than grounded in truth. Senior software engineers guide these systems effectively today without creating a mess. I'm sure in some years agents will fill the role of maintainability engineer too. We are not special or irreplaceable.
It's not like we won't be spending an incredible amount of energy to overcome issues with understandably and maintenance. The sheer economic forces will absolutely will this problem solved. It must be solved, because trillions of dollars urgently want it to be solved. That's evolutionary pressure if I've ever seen it.
Also, we ceremoniously ascribe too much value to the software we create. With the exception of a few places, almost all of it gets replaced before our careers are over. At the end of the day, business automation is value creation. It's not sacred. It has a finite life, and then it too dies.
The software artifact just needs to facilitate economic/interest flux long enough to be useful, then it can be replaced with something better or more relevant.