The biggest upside for me of having separate labelled mailboxes is I can use one, delete it later and never receive mail from it again.

My email addresses been public for years and spam was never a big issue.

But yeah it mostly opposite problem I would say - spam filters eat usefull stuff sometimes. Just today I found one more job related email in spam, but its from public mailbox damn.

Privacy is kind a bigger issue and having aliases on icloud is just much more convinient than having 10 accounts.

with something like cloudflare forwarding you can black-hole an address if it becomes a problem