It's a spectrum. You can replace someone to operate a cash register in a week. You can't replace a surgeon in a year, depending on how specialized and renowned. But sure, the majority of lower income work is more replaceable.

>but I bet you're not as irreplaceable as you might believe.

Given all the tech layoffs, maybe. But I think that has more to do with lacking either the money or interest to invest in certain products given economic forecasts.

The fact that your typical tech interview is a month+ and at least 3 (usually 5 or more) rounds of interviews suggest that it's not trivial to replace a dev. Tech is probably middle of the road to train, which is why they'd rather grab interns from college instead of setting up apprenticeships that can fine tailor towards the exact business needs.