And something people mention without mentioning everything else.
The existing system 'worked' because we grew from a few million to 8 Billion. If we 'stagnate' at 8, its no longer sustainable, therefore it was never sustainable if its only sustainable with constent growth.
Nonetheless, automatisation is not stopping anyway. We will solve a lot of theese problems with robots and ai. The bigger the problem, the bigger the pressure.
If the society is built upon the assumption of its own infinite growth in terms of population—an assumption which is very blatantly nonsensical—then maybe it deserves to break down.