The problem is that you are really dependent in what other people in your address range do. One malicious user in the same DC could reduce the reputation of an address range and then you get mail delivery problems.

I'd rather pay someone to sort out such issues for me. The $5 p/m or so I pay Fastmail monthly are far cheaper than my own time.

i have similar experiences. clean ip (actually from a hetzner block, but not on any lists), and dkim. I have never dropped an outgoing mail.