In any case, I can still find examples of these platforms. Emacs is such a platform. For that matter, StumpWM is a platform of sorts. A nice quality of Lisp is making any program extensible with it trivially. As for Ada, governments use it for critical systems and I can't tell you the particulars of those. They use Ada because people will die if the software fails, so they're seeking quality, not quantity. You're advocating for quantity, not quality.
As for APL, you don't build platforms or such things in APL. If you don't see the beauty in APL, then that's your loss.
They don't build platforms for others to build on, they build pillars to prove a point.
First you claimed people don't build great programs in these languages, which I've shown is false, and now you're arguing that they build things, but not things someone can build on. You're conflating extensible software with quality software here.
What actually happens with these languages is that a certain breed of highly opinionated but highly unproductive programmer gets lost in them, on their quest for a level of aesthetics or elegance or correctness that nobody but themselves actually values.
That happens, less so with Ada, but why would that even be a bad thing? Is it wrong for someone to spend time working on what they view as an ideal and finished program, rather than just writing something that's already been done and requires little thought or effort on their part? It's infinitely harder, I think, to write novel programs than it is to simply implement some specification or write a copy or something else. That's what I do with my work. I don't see why you'd look down on that.
I'll let you've the last word, if you want it. I'm not interested in replying in this chain any further.