I like the idea.... but this doesn't make sense.

I'm all for not using Google Analytics- I don't use it on my site. But why would you then use Google Sheets to hold the info? That's ridiculous. That's like telling people how to make an apple pie without sugar, and the last step before baking is dumping in a pound of sugar!

If you want an easy data store, use something like SQLite. There are plenty of options that are easy to self host, and a lot of libraries have been written to make it easier for you.