It is important to have program updates. However, they take time.
Most software applications that I have come across, give one the option to proceed with an update immediately, to cancel or to postpone to a later time.
Zwift does not give the user that option. One cannot use the game while the update in in progress.
The result is that I (and I am sure many others) have missed races / group rides etc. because of the time it takes to update the program. One usually logs in with a couple of minutes to spare (for a warmup) before a scheduled ride, especially if one is tight on time and trying to fit in some exercise into a busy life schedule.
Why can’t Zwift also have the option to postpone an update till later?
Not sure on this, but my guess would be that Zwift is trying to reduce the opportunity for riders to be on multiple versions of the app. By auto-loading the updates riders are, effectively, forced to be on the most recent version. There are already some issue with this, though, because iOS (and perhaps Android) users can turn off auto-updates.
As for mitigating the issue, I would suggest that you always start up your Zwift app before you even start to get ready for a ride so that if there is an update there will be time to get in installed before your event. (I do see posts from people talking about updates that take an excessive amount of time, but I have never had an update that took longer than the time to put on my kit and fill water bottles, so I’m guessing they are having a network issue.)
There is a possibility to switch auto-updates off.
I remember that there was a big outcry when the dirt sections got the increased rolling resistance added. Some Zwift riders were on that update and some were not. Needless to say there were some racers that were not too happy being on the update while others were not.