Well, I've gone to other games such as NWN. When I delved into the scripting, I found that there was waaay too much hardcoded, and thus got discouraged really fast.
I've always come back to UO, because I find the UO EMU's the best ones to work with to customize your world how you see fit. Personally, I'm making a shard for a target of 10-20 players, any more would obviously improve the gameplay (I've designed it so). But overall, I enjoy playing it, and eventually, hopefully many people will come visit, and join in on my server.
But in a way I agree with you, with RunUO and the ease at running it out of the box, makes it a candidate to get a shard up and running in no time.
Then again, until something as powerful as the EMU's comes out commercially, I have a feeling that UO is going to be around for quite some time in the EMU community.
I also think that people are still in the community, just not as active because they've all realized that RL is that, RL, and your hobby is that.
Oh well, not sure if I'm making any sense.