I have the same issue with an old ntlworld.com email address that can not be removed, and switched to other providers for email.
It is correct that the primary email can not be removed.
I get spam email most days on the old ntlworld.com email, but have set the email filters in settings to manage them better.
I also set up filters for the genuine emails which then go to a specific folder.
Regular spam emails from the same sender or domain can also be filtered out (see email settings) or sent to a spam or holding folder folder. The ones that keep changing the sender address still keep coming though, and VM sometimes tag as spam if the spam settings are to tag spam.
Beware of phishing emails and always check the sender address, and best to avoid clicking on links, images, downloads etc.
The dangers are if you give out your data to a hacker on a fake website, or clicking on a link or attachment that will compromise your computer or device, so best to avoid spam emails, but be aware of such things as identity theft attempts or using your email to sign up for goods/services etc.
As VM are phasing out the VM email service, it would make sense to allow deletion/de-activation of an old primary email, but they insist you have to keep it even it is a problem email, or insecure due to being breached in the past and on the dark web hackers listings and this means monitoring the email for security issues regularly.