Grafana isn't a Google Analytics alternative. You can build a lot of what you need with it (I've done that), but you still need to manage the actual Analytics part separately, Grafana only gives you the visualization.
It's okay, but I probably wouldn't choose it again. The ease of setting up Dashboards and Panels is great at first, but you pay for it with a low ceiling of what you can do (without building around it) and a "we trust everyone" approach to security.
Primarily the ease of use. You add the JS to your site and don't worry about anything else, collection is very fast (delivering data is < 30ms) and has edge-servers around the globe.
It's okay, but I probably wouldn't choose it again. The ease of setting up Dashboards and Panels is great at first, but you pay for it with a low ceiling of what you can do (without building around it) and a "we trust everyone" approach to security.