Talented, experienced devs leaving the field out of disgust would be pretty disruptive.
Crumbling, faulty technical infrastructure with unmanageable heaps of AI slop that no one understands would definitely disrupt businesses.
Skill atrophy, and an entire generation of "developers" that have never actually written code will be disruptive when something breaks and no one knows how to fix it (this isn't a hypothetical, I'm seeing this phenomenon in a lot of large enterprise groups).
The total elimination of novel solutions, new ideas and new approaches to development and the resulting industry wide stagnation won't be disruptive, but will certainly be a drag.
Replace "AI slop" with "legacy code", and you've got basically any large enterprise today.
The timescales are different though: it takes years if not decades to accumulate classic legacy cruft, while LLMs can spew up huge amounts of incomprehensible spaghetti in seconds.
PMs seem pretty easy to replace. In fact, given any single role to fixate on, it's probably replaceable
It’s because you are engaging in first-order thinking. You imagine the immediate result which is that software engineers are replaced.
If you engaged in second-order thinking you would realize that if software engineers can be replaced, _any_ work can eventually be automated. So why stress about it, we’ll figure out a replacement for capitalism. It seems like the world is starting the slow swing to the left so eventually the problem will be solved.
Of course might be those engineers you mention are engaged in no thinking.