The Creeper World series is in my opinion a hidden gem and features very satisfying and story-rich tower defense games, made by a single dev (“Knuckle Cracker”). I really loved Creeper World 3, but didn’t play the CW4, as I tried the demo and found that it’s laggy on my non-gaming notebook. The new part in the series, named Creeper World IXE, seems like it will use falling-sand-like pixel physics and a 2D side-view similar to CW2. The falling-sand terrain physics remind me of Noita, but will be interesting to see that in a TD game. I’m really looking forward to playing this!
I remember playing one of these as a Flash app when I was a teenager and I’ve never since found anything that quite scratches the same itch (or, like you say, ever actually met anyone else who’s played them).