I work in infosec consulting and reversing for 15 years. My identity has been compromised numerous times via OPM, Equifax, and Home Depot, just to name a few. I just don’t care about emailing sensitive docs anymore. I find an alternative if possible, which usually it works. I put in some effort. But realize emailed financial docs aren’t likely how you get owned. It doesn’t feel great, but it is what it is.

E: also, almost everyone I’ve asked will delete the documents after you try and fail to set up an expedient file share. Also, password protected zip files in Dropbox are usually good enough for most everyone and are a very simple system. Just make sure you use modern zip protection and not old crappy Zip crypto :)