I agree. It's extremely hard to learn to use someone else's spreadsheet unless they're sitting right there with you watching you fumble through it.
I have a couple of spreadsheets that I use on a weekly basis, and I found it easiest to build both of them from scratch, despite the tons of examples floating around for exactly my use cases, and despite it being my first time building anything with a spreadsheet in 10+ years.
On the bright side, after using these spreadsheets for a week, I lost all desire to write apps to do the same things. Google Sheets is a good-enough UI and solves sync across different computers and mobile.
It is also a very bad co-authoring tool imo unless you have a very tight team and processes of how to use spreadsheets. I would not mind if I was using it alone. But spreadsheets encourage a certain naive "visual" approach to structuring data in them that can become an issue if you want to import the data to actually process it somewhere and your coworkers don't really understand this well.
Spreadsheets can be useful, however:
1. Speaking about excel in particular, localisation issues are an absolute nightmare if you happen to live in the wrong country (commas vs dots for decimal points) especially while importing CSV files (which is already unnecessarily complicated in excel). If somehow you don't notice these issues, you end up with wrong data without understanding there the error came from.
2. If your coworkers do not really understand very well how spreadsheets work, you quickly get to become really frustrated with issues coming up when you have to import a spreadsheet for actual processing. Datetimes with different forms, coloured boxes being meaningful, mixtures of text and numbers and whatnot.
Yes a big part of it is "people problem" rather than "technology problem" but imo spreadsheet technology (excel, google sheets etc) encourages a variety of practices that make it less reliable. If the technology gives you the freedom to mess up too easily, imo it is not just a people problem.