I think this is largely why people complain that email hosting is so difficult. It’s not the hosting, it’s that so many people are doing it with a cloud hosting providers IP space. AWS, Azure, and Digital Ocean all tend to have their IPs in at the very least grey lists. Many home ISPs DHCP scopes too.

Getting a proper static IP, your own subnet from ARIN, or finding a colo with their own IP space will give people much better results.