It becomes less "write-only" as you build up experience. It's just not as readily learnable (if you're already a programmer) as most other languages. I mean, procedural and OO languages seem to have largely adopted a variation of Algol or C syntax with roughly comparable semantics to others in the same family. A programmer in C, Java, JavaScript, Fortran, Ada, Pascal, Go, Rust, Python, Ruby, etc. can mostly jump to the others and be able to at least read the program without much difficulty, though learning to write and extend the program (especially idiomatically) will take more time.
APL's syntax and semantics are much different so it has a larger barrier for getting to the level of reading or extending programs written in it, but it's not impossible to reach that level with a bit of practice. I spent a few months doing APL for 2-3 hours a week in the evenings and I was able to develop a reasonable level of competence in it (though not so much I'd drop it on my CV), I can still read it pretty easily now a couple years later and without really touching it since then.
APL's syntax and semantics are much different so it has a larger barrier for getting to the level of reading or extending programs written in it, but it's not impossible to reach that level with a bit of practice. I spent a few months doing APL for 2-3 hours a week in the evenings and I was able to develop a reasonable level of competence in it (though not so much I'd drop it on my CV), I can still read it pretty easily now a couple years later and without really touching it since then.