I still use it whenever I can
Wouldn't it be better to solve that problem? Proper generalized iteration with generators is just semicoroutines which can be implemented by swapping around stack pointers with zero copying. Should be competitive performance wise.
In the end, it's simpler to stay with boring, ANSI compliant solutions well optimized by compilers.
CCL, as far as I can tell, is abandonware
Last release was August 14 2024. For a 30+ year old project, that's quite recent methinks.
It clearly doesn't move as fast as SBCL, but I wouldn't call it abandoned either.
ototh, afaiu, SBCL gave up on ARM32. Can't blame them for that, but until 2023 I was still using an early Banana Pi with such. CCL worked there much better (also it's GC seems more robust).