I too have been online for 30 years, and frequently had ISP caused dns issues, even when I wasn't using their resolvers... because of the dns interception fuckery they like to engage in. Before I started running my own resolver I saw downtime from my ISP's DNS resolver. This is across a few ISPs in that time. Anecdata is great isn't it?
Your own "anecdata" shows how catastrophic DNS failures are and why it's justified to expect 100% uptime with proper redundancy. Too bad you had providers not architecturing properly this key part of their infrastructure to the point you had to build your own solution.
