Signal's devs, for better or worse, are very opinionated. If you don't do it moxie's way then you're doing it wrong. I was once shut down on HN by the Signal posse because I said that I'd like to have a Signal client library that I could use to write my own custom lightweight client. Apparently I'm not worthy and clearly incapable of writing secure code. Meanwhile I have to use that crappy, gigantic official electron app that cost them at least one serious security vulnerability in the past (JS injection, if memory serves).

If you want to make a nerdy niche chat client that's probably a good mindset, but if you hope to appeal to the masses you'll have to put some water in your wine eventually. I managed to convince a couple of my groups to migrate away from WhatsApp lately, but unfortunately always towards Telegram. Signal is just not there yet if you want a drop-in replacement.