I think you fundamentally misunderstood the potential issue.
Sure, on a reply based approach you can audit a DNS service.
But that doesn't tell you about other things like "is my DNS provider also providing intelligence agencies with my entire DNS query history?". The issue isn't "oh no the MI6 can redirect my PornHub link to anothe site", but "oh no the MI6 knows every single webpage I visited". Which is a valid worry given the current British political climate.
DNS is simply a look up service and yes, you do have to be sure of your sources. You can avoid the (sic) MI6 by using DTLS. Not sure why you'd bother though for everyday use.
That's not for the average punter but where there is a will there is a way.
I don't think that you live within the "current British political climate" nor do I think you know too much about it. Please feel free to educate us about your ideology and then we can usefully engage.