how is it not the case here?

Its like saying that titanic is unsinkable.

Our current civilization is optimizing everything, and with each optimization more people fill in the gaps.

If that machinery grinds to halt, the optimised mechanism stop. They dont slow down, just stop. And then things quickly collapse.

Thats how every previous civilisation failed, due to extreme pressure fundamentals broke and people panic.

'Oh but you are exaggerating, we survived a lot and lot longer since X civilization collapsed'.

We had global panic over toilet paper.

Not the person you are responding to, but I agree with you. Collapse is definitely on the table, at least in some form. But not an exponential decrease to zero.