This SimpleFIN blog looks dead - last article is from 2016. Not exactly encouraging.
I'm currently writing a library that implements SimpleFIN. While the main website hasn't been updated in a while (even the demo endpoints are out of date, and I've written to the maintainer last month about it[1]), the demo endpoint described on the Simplefin Bridge the docs still works[2] so hopefully there's still movement.
[1] https://github.com/simplefin/simplefin.github.com/issues/14
Plaid works great, but their API access is too pricey for an individual/small business.
Plaid offers transactions APIs (https://plaid.com/products/transactions/), but I guess to your point these APIs are geared towards fintech companies, not personal use.
EDIT: I don't know how well it works in general, though. You'd have to test it yourself.