Forth, (I think even more so than lisp), is fragmented, because its philosophy is not that you write “a forth program”, but that you write “a forth” that does what you need it to do. Don’t like the sign MOD chose to compute ‘-3124 modulo -17’? Don’t add a new one, but change yours. Need better approximations for integer goniometric functions? Change them to work in half-degrees, etc.
That makes sharing code difficult and that, in turn, makes it hard to write large programs.
Nowadays, I guess a ‘solution’ to that problem would be to run zillions of forths as microservices in a single process, but I don’t think that’s practical (could be fun, though. In the limit, one could give each forth a VM page of RAM or maybe even less to work in. Imagine a forth whose sole goal is to maintain and edit a string, with words for string indexing, search, replace, duplication, etc. that runs together with millions of other forths in a single process.