Well, I put "just" in quotes for this reason. My brother runs my mail server and I am under the impression he's doing it just fine as people usually do receive my mails but he's an expert in that sort of stuff, so yeah, I'd not like to just run my own server neither but some do and I'd use my brother's server a million times over some potential honeypot like proton.

just watched the presentation... lopp says there are gatekeepers, specifically those who manage IP addresses and domain registrars. I guess this can be argued, but this leaves hardly any decentralized system left. certainly Bitcoin core asks me what IP to bind to, and somehow fetches a list of IPs to connect to, too.

I manage and managed email infrastructure for many companies, certainly not the amount of daily emails lopp claims, but still a broad spectrum of different servers and plenty of traffic. i have never experienced emails being accepted and discarded on purpose by any mail system. the fast majority of mail that won't make it into the recipients inbox is usually blocked before even the body of the mail is transmitted or even the recipient was specified (DNSBL), thus leaving the matter to the sending email server. the consequences of false positives (legit mail being hell banned) would be grave, logs would show that the email in fact was delivered and it would be clear whom to blame for any legal consequences in most jurisdictions. I just googled those terms and also could not find anything about hell banning in smtp.

sure, the cost of running your own mail server is not zero, you need an IP and a domain and you need to invest some days from time to time to keep up with the development, configuring DKIM, which wasn't required before, but now many servers will reject unsigned messages etc., but that's just progress happening, it's not excluding anyone.

dynamically assigned IPs, unusually in dial-up scenarios are a real problem, I will admit that. but for me that's all that sticks from this presentation.