It will always be a dance. I own a small IT company in the UK and have always managed to run local SMTP. I've done it for about 22 years. I could not run a Mail Chimp.
For starters, I could not live with myself! I don't do spam. MailChimp is a spammer for hire by definition. Your idea of spam and mine may be different. OK: Unsolicited Bulk Email is the key phrase. At which point are you solicited or unsolicited? Opt out or opt in? Where do you get your lists and how do you monetize this beast? How do you vet your customers or do you even care? What standards of ethics do you ascribe to?
I could possibly create another MailChimp because I know rather a lot about SMTP and own a fair few IPv4s and could cycle them and I'm fairly IPv6 savvy so I'll use that to get some more mileage. I know DMARC/DKIM/SPF and all the rest and can play those little games to up the authenticity score.
Can't be arsed to spam the world. I prefer to host recipients than senders.