People generally complain about the interview process being bloated while also not giving a good signal - is it then not better to hire people for a while, see if they perform and then letting them go again? Though perhaps in Meta's case they hire a lot while also having cumbersome interviews, I don't know. I just feel like there are perhaps some benefit in being quick to hire and fire.
What people dislike is the boom-bust cycle inherent to all levels of a market economy. During some years, these companies suck people up like a vacuum -- that can be bad if you're on the inside and all of a sudden the culture goes out the window, or if you're expected to onboard 3-4 people at the same time, or you end up with a reorg every quarter. Then, on the other end of the spectrum, companies shut down (non-backfill) hiring entirely and layoff huge percentages of the company, with no guarantee that you'll be safe just because you're doing a good job.
Human lives do not work like this. If you're getting married, if you have an unexpected hospital expense, if you want to buy a house -- these are not things that "market cycles" will plan around, but you have to.
Being quick to hire or fire is not the problem. Massive overhiring and massive layoffs are.