For what it's worth, Emacs is an example of what you describe and it's extremely functional (and carries a huge amount of global state). Millions of lines, an insane number of contributors, development period of decades with a very decentralised management structure.
Emacs has a lot of problems but once you learn the base language, it's quite easy to interface with. I'd argue it's because of the limitations on structural complexity - you don't need to wrap your head around non-locally-defined structure in order to understand any one line. The parts that attempt to emulate OO tend to be a lot harder to deal with as an outsider.
Emacs has a lot of problems but once you learn the base language, it's quite easy to interface with. I'd argue it's because of the limitations on structural complexity - you don't need to wrap your head around non-locally-defined structure in order to understand any one line. The parts that attempt to emulate OO tend to be a lot harder to deal with as an outsider.