The problem is that SL is closed source. I once tried to run a virtual field trip with 10 kids to show them around, but Linden Labs blocked us for having too many users access SL from the same IP address. You have to lease property on Linden Labs servers for a presence there. Why am I going to invest the time and energy into building something amazing on rented space that will vanish the moment I stop paying for it?
If SL were to be released as a open-protocol, like WWW, where anyone can pop a server onto the Internet and host a community, I think SL would thrive again. I would love to see that.
I found a nine-year-old blogpost I wrote on the science attractions in SL. It really was an amazing place. I would really like to see something like it again, but open. I think there's a huge opportunity there for someone with the right technical capabilities.