To the level where you can spot windshifts, more pressure, notice that your sails are trimmed wrong, wrong weightplacement etc. on your own, can start self-coaching and really begin to learn how to work your way up the fleet.
Everybody can learn of course (poor choice of words earlier), but if you dont get systematic followup, getting to this level on your own takes time and lots of work.
I learnt to sail this way, working with a friend on our own and by reading whatever we could find of literature (Your and Ricks book was a treasure when we found it). I am quite sure we could have cut a year or two off our learning curve if we had been part of a course, club, or something. As it is, we have not learnt how to go fast until the last couple of seasons, and still get surprises in certain conditions.

Oh yes, the boat we learnt to sail on was a classic Tornado with sails from the 80's..