A good h2h limit strategy probably plays 95% of buttons and 70% of big blinds or so, so at least 30% of the hands you play are neutral EV at best (symmetrical game, so at most 50% are +EV preflop and you play at least 80% of all hands).
Only playing hands you are +EV against a full range would be exploitable as it is way too tight in heads up.