I really like the approach and vision. However my initial reaction: Why do I want a generic taxonomy for events? Every business has their own domain. Generic click events are not really interesting, but more domain specific events are.
For example for github you would want events like "project.Starred" "project.Cloned" etc. OR for hacker news "user.addComment" comment.Upvote etc. So you would need to build your own taxonomy anyways right?
I do see the potential power of using BI tools that are built upon a generic taxonomy.
Another comment: I don't really like using "TrackedButton" components that replace Buttons. What If i want to use Next.js and want to use the Next.js's Link... It's better to have a "TrackedObject" and embed a Button inside it..
Maybe i'm too used to calling an "analytivs.trackEvent" function manually coded, because we mostly used company defined events.
If you want open source, using SnowPlow + storing it in redshift using a pipeline would also work. But I guess with Objectiv you don't need to setup anything..