I've found that "send me a spreadsheet and I'll upload it" isn't a great user experience. It's just a big pile of cells, with no documentation (which they wouldn't read anyway).There are a billion things they can do wrong, and they get no feedback on it until I email it to them. They don't know what the options are for any field, and it's easy to enter a nonstandard value. A typo in a header row can lead to data loss with no errors.
There are times when it's the easiest way to handle things, especially for experienced users. But I find it a massive hassle to maintain support for every possible mistake the user can make.
It could work but there is still a bit of developer overhead: (1) Use iron-clad schema validation in the database; (2) Provide some forms over top the Excel data like old Access applications.
The benefit would be that you have a fixed set of UI components available in Excel and don’t need to worry about styling and whatnot.
Fixed drop-down fields are very helpful for shared/inter-company spreadsheets too. Highlight them in red until they're changed, then enforce the value via dropdown.
There are times when it's the easiest way to handle things, especially for experienced users. But I find it a massive hassle to maintain support for every possible mistake the user can make.