tl;dr What applications (web or desktop) have you seen that have excellent, productive user interfaces that prioritize getting shit done?

I am currently developing a moderately complex web application with a management interface that will be used by non-technical users. It also has a separate interface for technicians to see their tasks and submit reports, but I'm pretty happy with how that's coming together. I have a pretty good idea of how I want to display data in terms of what kind of "widgets" I could use. For example, a calendar view with daily, weekly, and monthly view modes. What I'm looking for inspiration with are the finer details, like filtering data, navigation, data hierarchy. I want to find things I hadn't even considered and aren't part of the typical "flat web UI toolkit" playbook.

I'd love to steal small ideas from a forgotten tool built for Windows 95, or maybe those paradigms are best left in the past—I don't know. Personally, I find most flat UI applications are almost useless in terms of discoverability, productivity, and general ease of use. Something like the Azure dashboard is what I would like to avoid building.

I'm also trying to keep my front end stack pretty lean by using Vue.js and rolling my own components based on accessible and keyboard navigable HTML components.