We do seem to have a nicer depth to canon backstory that allows for things not seen in the show (being a 90's creation, I'm not surprised that the closest we got to gay-anything was Carter Wellan et al. and that was pretty low key), but I don't think that stopped the need for those first two waves. Highlander is hip-deep in first time stories. I think the chemistry of first romance like that, an OTP type pairing, is just highly charged. It's only been in recent years that DM/Other or M/Other has picked up any steam. I distincly remember jonsing for it way-back-when and finding very little of it, so much so that I had to write my own.
Is the first-time story dead in the water? I can't think of a single new slash non-crossover first time story that's been posted recently. (And yes, I am lazy, and have not gone to look in the flash.)