At a former job I had to build a reporting system. And had the trust to build it however I wanted. But it was my job to make it sufficiently useful that everyone would use it.

The smartest thing that I did was make it accessible from Excel. You could build a spreadsheet off of my report. Refresh the spreadsheet, the report ran, you got updated data.

I got essentially 100% adoption, and the rest of my job was spent finding people who needed data and adding it as an option to the reporting system.

Usually you expect a complex reporting system to have features like graphing, pivot tables, etc, etc, etc. My answer to all of that was, "You can already do that in Excel. I could spend a lot of time on it but I'm not going to do it as well as what you already have."