You are obviously not reading what people are saying. They are not coming via e-mail. Any idiot knows to delete an e-mail. These are events that are showing up on our calendars, that WE did not put there. The only option it gives is to decline, accept, or maybe. If you decline, they know it's a working account and will continue to bombard you until your calendar has spam, filling the whole day, on every day of the month.
A temporary workaround is to go into calendars, click edit, then click add new calendar, create a new calendar and name it SPAM. Then go to the event invite, and click on the name of the calendar that the event was sent to (example: Home), now choose the SPAM calendar instead, and it will move it to that folder. Then go back into Edit, and delete that Spam folder. The calendar event will now disappear.
You can also go into Icloud.com from a laptop/desktop, and click on calendars, then settings, then advanced. Check the option to have event invites sent to your e-mail instead. Then, you can easily delete the e-mail without replying, or just report it as spam.
I have spent hours on the phone with Apple for the last 2 days, talking to supervisors in the tech department. They said they were going to forward the info on to the engineers. They told me to call back in a few days and tell them if it was still happening.
P.S. They did not know about the workaround, I found that on my own. They also didn't know about changing your Icloud settings to send invites to your e-mail either. I found that myself, online. They have no clue that these are related somehow to Icloud.
Also, if you click on calendars and look at the list of calendars, such as "Home, Work,& Calendar"...if you click the little "I" for info on the right, then where it says "Shared with", click "Add person"...and you will see the actual e-mail addresses of the people sending these invites to you. They have shared access to all of your calendars, even if you create a brand new one.
Apple is going to have to create an option/security setting where you can choose to NOT allow anyone to access your calendars, unless you specifically send them an invite! Strangers should not be allowed to access your calendars by simply knowing your e-mail address!