I encountered this late last month. Got a spammed for months worth of day-long events where the description was in Chinese. Fuck declining each of them individually.
Apple needs to just let us block all requests unless they come from a known sender.
After having two iPhones in my family remotely locked by (assumingly) Chinese e-mail accounts, it's clear that something on Apple's backend is completely compromised.
Throw me into the bunch getting them. I noticed they were coming from just two so I created them as contacts and then just blocked them but we'll see if that works or not.
Apple should just remove the uselsss feature all together. If an appointment is really important you should be able to put it in the calendar manually like a normal person.
The social media team at @AppleSupport had me call support yesterday after I complained about this, but since there isn't any fix, it was a solid waste of my time.