You shouldn't need to "Learn Excel" if you are a programmer. You use Excel or Google Sheets or Emacs' "Simple Emacs Spreadsheet" (SES) or whatever tool to do things you need to do, and learn whatever features you need as you go.

I personally use Google Sheets for: - Impromptu project planning and release tracking in small teams - Creating test plans for release testing

And not much else as I can do most other things using other tools. If you want to pivot data and do data analysis, yeah you can use a spreadsheet. Or you can use python.

I wouldn't go out of my way to learn the deep depths of excel when you could take time to learn sed or awk or columnar and multi-cursor editing in emacs or other tools that, beyond tasks that can be accomplished in excel, will help you in a wider variety of tasks.

But by all means I would be using excel for simple spreadsheet things. It's not a tool I'd go out of my way to spend time on learning excel as a programmer without a task infront of me as being a curious technically apt programmer means it's quite intuitive and fast to learn whatever I need to accomplish things in excel as I go.

Learn emacs, learn colemac, learn awk, learn clojure, learn pandas. I don't think you need to learn excel beyond basic spreadsheet functionality.