What exactly is a marksman nowadays?

I remember a day when marksmen were mostly non-mobile, lacking of CC, champions with some serious sustain damage potential when properly peeled for.

Marksmen have evolved, and whereas that's not necessarily a bad thing, several have become... well..... burst mages that farm REALLY well.

Call me old fashioned, but you should never be bursted by a marksman unless it's absolute late game and they have 100% crit and 2.0 attack speed.