> The fact that on Earth the living beings eventually used ATP and RNA appears to have been determined in great part by chance, while the use of amino acids seems to have been much more deterministic.

It looks like on Earth the RNA was the initial replicant. RNA can be folded into complex shapes and can have catalytic properties in itself. Ribosomes that assemble proteins have RNA at the active site with proteins only providing structural framework.

That's why amino acids might not end up being so universal.