I think for many/most customers, the sync is still working fine. Sync and iCloud are always going to have some issues. That’s the nature of the technology, which involves many complex systems working together.
So I wouldn’t assume that iCloud is broken for all customers on 15.2. That would be a major issue for Apple. What may have happened is that some customers are meeting with an issue that was introduced in 15.2. (If you search Reddit any day of the week, you will probably find many iCloud issues. When you consider there are probably a billion people using it, you can easily find a few hundred with issues on any day.)
My advice is to get in touch with us if you are having sync problems with Agenda and iCloud. We can usually sort them out one way or another.