Milsim is a very broad term, you've got the sort of stuff that gunman and ambush adventures do where it's essentially a well organised skirmish with team kit colours all the way up to stirling and tier1 games where you start at midnight with a full brief followed by a dawn assault to take your team's 'FOB' (if you're on the good guy team that is) followed by 36-48 hours of game without programmed breaks and no safe zone.
The former I would say is eminently suitable as a starting point for any airsofter, the latter normally takes a bit of working up to as the kit requirement is normally a bit more substantial (Bashas, ground mats, cooking kit, a couple of working guns in case your main one breaks, night vision, etc).
That said, the only elitism I have EVER experienced in airsoft is reverse snobbery where guys have had a good old chuckle at the idiot who spent £2k on night vision to play soldiers. Each to their own I say!