The system I'm typing on runs Windows Server 2019, which has the Windows 7-era calculator and very little ability to use UWP apps, and I still do my math with Speedcrunch, Desmos, or an emulated TI-84 Plus CE via CEmu.

The Windows 7 calculator is a solid basic calculator, but I think most power users in that time used third-party options or something like a spreadsheet. Microsoft clearly thinks of the calculator as a demo application for UWP and XAML, as evidenced by them open-sourcing it, sort of like how Apple treats TextEdit like a Cocoa text rendering demo. If you want a serious calculator or a serious text editor, you're better off looking outside these bundled tools.