The book Dreaming in Code [1] goes into great detail about how CalDAV (and WebDAV) came about through the work of the group who built the Chandler calendar program (or tried to). It’s been a while since I read it (at least 15 years), but I think it partially discusses some of the ways a protocol like this can get lost in committees during the design process. The fact that this project started around 2001 should also be informative about how long calendaring has been a problem. So, if you’d like to know about why it sucks, I’d recommend it.

It’s also a good story about the conflict between startups and open source, building products, and software development in general.

[1] http://www.dreamingincode.com/ ; https://en.m.wikipedia.org/wiki/Dreaming_in_Code