I trust CF much more than my ISP, but it makes the potential leak much worse...
edit: On the other hand, DoH makes DNS requests independent of ISP, which is nice. ISPs are often monopoly by nature.
Obviously, for Thai users this is a reasonable option, but I would understand why American users would not want to use Cloudflare, Google or even Quad9, as these are all US-based.
HQ
1442 A Walnut Street
Suite 501
Berkeley CA 94709
Bonus if you are interested: forum thread where Quad9's director of the board comments about DNS are surprisingly informational.
They are, but because this is all Cloudflare's 1.1.1.1 service does, that log only tells you that the IP address used Cloudflare's service.
So whereas this Thai data more or less says e.g. You watched Netflix between 18:40 and 19:26 and then again 21:33 to 22:09 the Cloudflare data says you own a device that uses Cloudflare's 1.1.1.1 DNS service. Maybe you can try to do some kind of activity estimate e.g. me idly browsing random web sites probably causes more DNS queries versus a SmartTV just periodically doing auto-updates when I'm asleep, but the 2000:1 dilution would make that more unreliable.
It isn't strictly nothing but it's damn close.
It is much better than just having normal logs laying around, and since the data is split in two data set, there is a possibility that having access to one does not automatic result in having access to the other. The dilution is also helpful, through I am uncertain to the extent given the amount of traffic generated.
For example Facebook probably said they would keep your data secure, but their system to prevent abuse from 3rd party "Quiz" developers was "Developer, by clicking here you agree not to abuse the data you can access."...