Having said that, I host some of my mail with Hetzner, and even at their scale they sometimes have deliverability issues.
A warning that hosting e-mail yourself can be difficult, is very useful, but the suggestion that you should not do such a thing is not.
I have been hosting my own e-mail since 2004, for more than 2 decades and I do not intend to ever give up on this.
The cost of hosting my e-mail has been absolutely negligible and for most of these 22 years, the time spent managing my (FreeBSD) e-mail server has also been completely negligible (perhaps an hour or two per year, on average).
A good mini-PC, e.g. an ASUS NUC, with a negligible power consumption when it is operated 24/7, is completely sufficient for hosting everything that might be needed for Internet access, e.g. router, firewall, NAT, NTP server, dual DNS servers, DNS proxy and cache, SMTP server, POP3/IMAP server, HTTPS server, Web proxy and cache, DHCP server for the internal network, etc. On a mini-PC that does not come with enough Ethernet ports for your needs it is easy to add many more ports on USB.
It is true that a few years ago I have encountered enough problems with stupid e-mail servers configured to automatically reject as spam anything that does not come from a huge company like Google or Microsoft, but thankfully during the last couple of years such cases have become more rare, not more frequent.
It is a great hobby, and a good way to keep aware of current trends in internet infrastructure. And, like riding a bicycle to commute, maximally free of red tape or external regulation.
I should be able to refuse emails and not get spammed with life ending phishing and malicious links around every corner.
Email providers shouldn’t be able to whoopsie and delete emails on my behalf, or gatekeep information that’s needed in court.
Self hosting doesn’t fix the core problems with email even if you don’t screw it up, which you will.
Phishing and malicious links exists on every kind of messaging - email, forums, whatsapp, telegram, SMS... you name it, it has spam/phishing. You'd think that at least "real name" or "pay a bit per message" might discourage this, but example of SMS (text) shows otherwise.
With any system the server operator will be able to delete messages, and/or gatekeep information - unless you have some sort of "big brother" setup where every message goes through government-operated monitoring server, and I cannot believe anyone intentionally choosing such a system.
(steps on soapbox) And as long as we are talking about SPAM, why in God's name if I block a text message and then the phone number from ringing is there an additional block required to prevent voicemail? Oh, I see, it is so Verizon and others can charge me to block voicemails. Even on Google FI, if I block a number on Messages it doesn't carry over to calls which doesn't carry over to voicemail. Enshitification. (steps down)
Basically you had to play a (very small) amount to charity to cold-email someone (and with an escape hatch if you state you know the person)
That system would basically gate all spam without changing much
If you want to deal with the background radiation firsthand that's your prerogative, but it's like growing your own food. Unless you're committed, there's no reason to not just use the grocery store.