Sheets is capable enough for the average person but a business is always going to want to use Excel because it's the industry standard.
I can't remember the last time I actually needed a spreadsheet for anything other than looking at a bunch of tabular data, but I'm a programmer so I'm not the standard spreadsheet user.
JSON files that get committed to a git repo, obviously. They're in a private repository in GitHub so that takes care of security and resiliency, two birds with one stone.
Nothing compares to excel. There are spreadsheets, and there is excel. The world runs on excel, and for a damn good reason. Also, excel runs the world, literally.