I’ve been using it for around the same time, and never cared much about formatters. Linting is useful but wouldn’t call it essential. But type checking is a non negotiable on any project I lead. It’s not perfect by any means, but beats having to crawl my way through a call stack trying to figure out what the hell a function is expected to take and why it’s getting a None instead.

I have yet to find a single drawback of adopting mypy (or similars) that isn’t completely eclipsed by the benefits.