Now they are just large advertising platforms that do something to attract users and user data.
I think under similar logic, if you want to work for those companies for comp/prof development, it’s probably whatever next money printer is building out.
IMO this is probably AI, next-gen adtech that keeps the technology going post-GDPR etc (platform plays like FAANG or great user enumeration companies in the open ecosystem, although a lack of a non-obvious adtech product might limit the growth and prestigious of these types) maybe some top cybersecurity vendors if the problems get worse and regulations get serious, maybe defense tech (second gen ones following what Palantir did).
My personal preference and risk appetite takes me to successful small public companies or well-funded startups.
If I don't have a risk appetite, I'd go government or boring F500 companies that are starving for engineers.
Wherever I go, I am very particular about the mission and that I get along with the team and manager. The less the bureaucracy, the more likely I am to enjoy working for them.
But there is no way I will work for big tech with their miserable processes, culture and exploitative management. I am here to work, not to constantly walk on eggshells for BS rules.