It has been argued, I wouldn't say that it has been shown. Both my ISPs operate a DNS blacklist. So did my previous ISPs, in the country I previously lived in. And in a third country, where I was on holiday. ISPs even in the USA are gnashing their teeth at the prospect of losing visibility into DNS. Why would they care if they weren't using that data? Why do they need a subscriber -> [domain] mapping? Routing tables don't care about domain names. Edge caching of web content doesn't work with https. I might care about DNS caching if the ISPs haven't demonstrated time and again that they will abuse my privacy for a buck, after I've already paid them for the privilege.
I trust Cloudflare much more than I trust any ISP I've had to deal with, including American ISPs when I lived there. I trust Google much more than any ISP, and I'm not particularly charitable towards Google.
Centralized DoH isn't perfect, but it's better than the status quo. The SNI hole is shrinking. My threat model does not include defending against the Mossad doing Mossad things with my email^H^H^H^H^HDNS[1].
[1] https://www.usenix.org/system/files/1401_08-12_mickens.pdf