I agree. I am (or was) looking for alternatives to move from bluehost VPS, in part because of email deliverability and their issue with DKIM records. Now that I have SPF, DKIM and even DMARC set up on a droplet (and tested the authority), gmail still spams the server outbound emails because of the rDNS issue with floating IPs. Pretty much every server I run sends out email, and some are web stores. Makes little sense to move if the server mail doesn't get to the users. A large reason for this was not to force my clients to use some other mail alternative for simple server messages.
If there is a way around this I'd love to know, it's down to this one detail. Floating IP's mean Digitalocean droplet scalability and staging. rDNS (along with SPF, DKIM and DMARC) means the emails don't get spammed.
Basically what this seems to say is that you can't really have scalability features of floating IP's and still expect outbound server mail to get to anyone's inbox.