does that also work with xlsx files without much pain?

Nushell has it built in: https://www.nushell.sh/commands/docs/from_xlsx.html

Powershell can query excel files in various ways and there's a module for native powershell excel work: https://www.powershellgallery.com/packages/ImportExcel/5.4.2

Fascinating, is there something like this for Word?

Morning built-in I know of. There's COM or pandoc, but you'd need to script that yourself.

That's great. Is there something like this for MS Paint?

You can only print, I think, with MS Paint from the CLI. ImageMagick is what you're after if you're working with images from the CLI. No expert though.