I know it's a lot of fun writing Forths and that's how most people tend to experience Forth, but I like to urge people to actually build applications on Forth. Understanding Forth by writing applications is probably the best way to get a feel for Forth.
gForth is probably the closest you'll get to a batteries-included ANS Forth. It has a lot of libraries and does have some GUI libraries. It definitely has networking and some amount of db words, I'm not sure what it's concurrency situation is like.
8th is a great not-Forth. Highly recommended because of how practical is.