Zuck-a-bees need to get in on the ground floor of the next, next big thing, which barely exists right now.
And the next wave after that is already happening, but you'll have to figure that one out on your own.
Everyone always thinks they're at the end of history in one way or another. Saying that current big tech companies have reached a critical threshold and will remain static for a certain amount of time is like watching a stock price go up - you may think it's a sign that it will continue growing, or that it's peaking and will go down, but you can only say that with certainty in hindsight. Nassim Taleb would go as far to say that there are much less actual underlying trends, and that more is governed by randomness than you think.
In terms of emerging technology, growth and consolidation is a pattern that happens throughout history, and the current state does appear to match that pattern, but this situation is more volatile because the big companies don't have as much physical assets which vastly changes the ability for smaller companies to compete (source: capitalism without capital).
I am not saying it is easy, far from it, but the idea that there is no chance for unknown person/companies cannot grow to establish themselves as giants is ludicrous.
Crypto is the next thing.