Lean and most type theoretic-based languages don't merely preach simplicity, they demand it. A function or type with a handful of terms or constructors might be provably inhabited/total, whereas one with 2 handfuls of terms or constructors might not be in a reasonable amount of time due to the exponential growth of the proof space. Factoring code optimally for provability yields the simplicity that Forth programmers are striving for.
As the saying goes, once you've seen one Forth, then you've seen one Forth.
I've mucked around with my own Forths in the past, including one that recognises lexical type, so you could build something like a parser in Forth. I didn't take it that far. Forth is normally conceived as being built from the ground up, but if you're you're going to implement it in C or C++ then you can be more imaginative.
I played around with colorforth for 5 minutes on a couple of occasions, but I ran away screaming. What - just what - the hell is going on? I'm sure it all works for Charles Moore, but for mere mortals it might as well be a klingon control panel.
I think Moore effectively gave up on programming a couple of years ago? There was some strange modification in the guts of Windows and he couldn't get his environment to work any longer. He concluded that the game was not work the candle.