Only true if your audience doesn't require Edge distribution, also if your Origin can handle the increased load and security issues, also if you don't use any advanced features (routing, edge compute...).
Yes, and they come with different architectures, SLAs,... not so easy to pick one. Their features may not map 1:1, not so easy to implement a multi-edge solution.
People are ready to switch to third party but such plan comes at cost.
Instant switch means really high cost (two contracts) and also maintaining and testing it regularly. Also means you are limited on advanced features and most likely stick to basic features, reducing your ROI.
Most people are ok with a switch that would take days to weeks, reimplementing basic stuff during initial migration, then iterating on more advanced features. You run at risk to be down for hours to days. The cost of 2N or 2N+1 vendors is just too high to justify it.
If your site is only hosted on one server and it catches fire, you can swiftly reinstall on a new server and change the IP your domain is pointing to, too... Still a single point of failure.
Yes, everything in the world is a single point of failure and has always been, if we look at things that way. But if it can be remedied quickly, then it's not a huge concern.
If I had pointed my name servers somewhere else, then that of course would be the new single point of failure. You can't escape it, no matter how much hacker snark and down votes you have.
