The "a lot" part is emphasized. It has to be something massive? Classes? Objects?
With the same token one can say most other languages lack a lot as well. That "lot" would be fault tolerance. Notice how most operating systems today use isolated processes instead of sharing memory like Windows 3 or DOS did. There is a reason for that. When the word processing application crashed, it would take down the calculator and media player with it. So modern operating systems have isolated concurrency units. And so do languages built on BEAM VM.
And of course you could still spawn OS processes and run a language that uses shared memory between its concurrency units (threads, goroutines, callback chains). But you can't spawn too many. Or even worse, everything has to run in a container, so now you have a container framework as another layer. And the question then becomes "how many layers of abstraction can you add to an ecosystem before it is unusable?" ;-)
> Elixir is trying to fill those gaps, but how many layers of abstraction
Elixir is not built on top of Erlang the language. It compiles to the same BEAM VM bytecode. But the intermediary representation layers between the running bytecode and the language syntax was already there. They didn't add another layer on "top" so to speak.
> They embraced actor model,
Don't think so. The creators at the time had no idea about the actor model. They embraced fault tolerance, concurrency and low response time most of all.