Totally agree, though ironically Claude code works way better with Excel than I expected.

I even tried telling Copilot to convert each sheet to a CSV on one attempt THEN do calculations. It just ignored it and failed miserably, ironically outputting me a list of files that it should have made, along with the broken python script. I found this very amusing.

Think why an LLM might really struggle with csvs. You're asking a chat bot to make a weird sentence with tons of commas in it.

I've read that they're supposed to be great with XML as it's so structured, better than JSON, but haven't actually found that to be the case.