Or unless your emails matter to your customers, with you seeing them as individual names instead of spray and pray marketing.
Deliverability is the single most important thing to reach individuals in the first place, even more critical to maintain the transactional or workflow email relationship.
Anthropic right now has an issue where their "passwordless" emails go to junk for M365 customers (85% of SMBs in U.S.), people literally can't use the service since the email isn't delivered to the inbox.
To your point, in a past gig helping thousands of businesses with turning contacts into not just buyers but fans, I discovered mass marketers don't really care about deliverability at the level of "every single communication must land with every person".
At the same time, I learned customers you want to build a relationship with very much do care. Ever since, when evaluating these, I start there, even before price. How many communications, transactions, or workflows with a future buyer with intent are you willing to fail to connect?
"You had one job" means the primary, not only, dimension. Yes, the primary job of a mailer is for the mail to get there.
I agree there's lots more to look for as well!