It is total b*lls for ATC or anyone else to suggest that GA should not use large airports since GA is all about going on a 'jolly'.
90% of all aircraft passengers are flying on a 'jolly', usually holidays.
I can appreciate the operational difficulties of mixing small, low speed aircraft with large high speed ones, but let's lose the 'GA is just for fun' criticism. Virtually all flying falls under this heading. (And what's wrong with having fun anyway...?)