The Sicilian's standard first few moves exchanges White's center d-Pawn for Black's c-Pawn and begins a process that usually leads to a strong Q-side position for Black. Consequently, even if you don't play the book moves for the Dragon, Najdorf, etc. you should be able to achieve a VERY playable middle game for Black even if you're a club-level player.
Of course, that means NOT memorizing reams of opening moves but studying the ideas behind the Sicilian and understanding opening principles strongly!
The truth is a bit different:
One slight slip in the main lines of the Dragon, or Najdorf, and you will not get a chance to make another.
@SmyslovFan,
so, when is the appropriate time to play sicilian as black according to you?
I don't agree with you that postponing the playing of sicilian helps the improvement(especially, if someone has ambitions to be a master or higher). On the contrary, I think it would be counter-productive to avoid sicilian. Because the later one starts, the more difficult it is to adjust to an opening like sicilian and also learn all the theory in one go. The earlier one starts, the easier it is to adjust to the opening (and get feel of it) and learn the theory as one goes along. So, I would say that one can switch to sicilian somewhere around 1400 and slowly ease into it rather than getting into it later and finding it hard to adjust.