It won't kill them, but it will slow down Meta for a while, during a critical period where it needs to outrun innovation that will be nipping at its heels through the 2020s. It could be one of those "causes of the IBM-ification of Meta" in an article you read in the 2030s, but it will probably be more like, "the pandemic caused Meta to overstretch, at a critical point in its history and the history of technology, and [along with other companies] suffered as a result in multiple ways."

On the other hand, in the current environment, I can also see a lot of people figuring that they're not going to improve their prospects elsewhere in the near future so, since they're apparently at least somewhat valued given they're still there, they might as well just keep their head down for a year or two.

Oh absolutely, some of the mediocre employees will stay because of that. The exceptional ones are still going to head out for greener pastures though.

Eh. It's at least a more challenging environment for being hired in tech right now. Assuming they like their work and are getting well-paid, why should they move?

Because the local environment is going to get more and more cuthroat and backstabby as people feel pressured.

And this is different where exactly? If Meta does another round so will Google. If it’s layoffs or ChatGPT the only thing Sundar knows how to do is copy/paste. Amazon and Microsoft are already PIP culture.

It's different in sectors which aren't going to go through some things, places which are expanding rather than freaking out about dropping ad revenue and the end of zero interest rates. OpenAI / Microsoft, various energy sectors, and Palantir / miltech come to mind.

Life in a contracting industry sucks as a general rule, Meta has presumably decided that shedding weight is worth the nth-order effects. It's a strong signal to move on or start cultivating new skills now IMO.