This might as well just be a PDF. The source format shouldn't matter if the recipient is just going to read it.
> architecture descriptions, requirement definitions
A hierarchical plain text document (biasing towards Org if you want internal links) would satisfy the same use case and play much better with source control.
> Using a database and scripting is overkill for 90% of things and is just over-engineering a problem that spreadsheets already solves well and are understood by the people who are meant to read them.
It's not a binary. I don't particularly like Python or SQLite, but I'd take a couple of quick and dirty Python+SQLite scripts over a bunch of unstructured spreadsheets any day.