Alba and Busquets will be impossible to replace 1/1, even though they have great players able to play the same position. Their styles are unique and bring a lot to the team, but of course they both have their weaknesses, too.
Dreaming about adding someone like Ramos is a bit stupid I think, you have to take everything into account. It could just as well be him missing that made Spain play the best football of the tournament and their best football in years (and of course there could be a similar reaction when Busquets and Alba are gone). Enrique made a few pretty brave and unexpected decisions and they mostly seemed to work. Fati would probably improve the team though.