Your experience is very similar to mine. I got most of my early programming chops doing C programming on a MUD. I also had the experience of a very religious mother throwing away all of my DnD / fantasy related games, because of the craze about satanic symbols that swept through the US in the late 80s/90s. I wish my kids would play DnD together - I can't imagine a more wholesome activity to be honest. Haha.

I also much more enjoyed MUDs than WoW and the various mmorpgs. There was less polish, more "secrets" that only a few people knew about, lots to explore and discover and things always being added. The games felt organic and interesting interactions developed simply because the logic was not locked down (including bugs that lead to interesting behavior). I enjoyed WoW, especially with friends, but it felt a lot more like a skinner box with nice graphics. Nothing in it ever compared to some of the epic experiences I had on MUDs.

I would concur with others here that the sandbox environment of Roblox is pretty awesome. My son especially gets up to all kinds of crazy creativite stuff - like making a TIE fighter recreation and various Boeing models in Build a Boat for Treasure. Like MUDs of yore, there are plenty of bugs and lack of polish that make things even more interesting.