Bottom line, with stock payment, you have a say in their ultimate value. Do good work, company value invreases, you enrich yourself.
Statistically speaking, they're correct.
Recently learned this from the excellent and very pithy Michael Batnick blog https://theirrelevantinvestor.com/2020/09/10/most-stocks-suc... who was citing https://wpcarey.asu.edu/department-finance/faculty-research/...
If you can’t afford a single but if variance then I guess RSUs won’t make you happy. But for everyone else they work just fine (unless your company goes down in flames, in which case you have bigger problems and are probably job searching anyway)
If you keep the stocks after they vest then that is your fault for keeping them instead of selling them.