> Over time I realized that residential IP blocks were banned on most servers. > You just cannot create another first-class node of this network. > Email is now an oligopoly, a service gatekept by a few big companies which does not follow the principles of net neutrality.
It's unfortunately true. However, the reason that how we end up like this is more nuanced than just the big players trying to power grab (perhaps) but rather because of the rise of spam/scams/phishing/malware. All big players like Google (Gmail), Microsoft(Outlook/Live.com/Hotmail), Yahoo!, Apple (iCloud) are suffering from those threats, wasted bandwidth and compute on spam detection heuristic AI.
There are industry consortiums like Spamhause and commercial entities like Barracuda to maintain blacklist/whitelist to restrict access of major MTA network interconnect to fight off spams/malwares/phishing/malware delivery from botnets and individuals. And it helps, at the mean time, it consolidated the control of who can send outbound emails.
We are seeing this trend repeatedly in other communication channels like phone calls (due to robocalls, VoIP numbers are being blacklisted by all major players' services) or Text messaging (due to spam texts, major U.S. wireless carriers band together established Campaign Registry to control who can mass send outbound text messages. This is also known as 10DLC registration).
I think the vulnerabilities of previous communication protocols (email, VoIP, SMS/MMS) lie in the fact those protocols are designed with security in mind. Modern community protocols like Push Notification has been designed with security in mind, which make it less susceptible to abuse and spamming. That's probably the way go forward.