It's not because of the gameplay: it's great, and I'm glad nades are gone. It's not because of the graphics: love em. Even the sounds are great.
But one CTF map? CTF is the meat of TF. I would have even been happy with the old Well map, but they had to go and change that to something unrecognizable, too. I'd be happy with a new CTF map, but all we get is 2fort.
Want to know why so many 24/7 2Fort servers are popping up? Because people want to play CTF. The defend/attack control zone maps are decent and worth playing, but they're simply no replacement for the encamped defensive bases that define CTF. Having two teams on defense and offense is much more balancing and fun than having one team perform one function and the other team the remaining.
I know more maps will come, both from Valve and the community. But like Portal, Valve stopped at 'good enough' too soon.