DoH in itself is not sneaky, no more than ping is.
The push to centralise DNS resolution in the hands of a few questionable actors is and this is what is happening.
Cloudflare for example would absolutely love to know what you're up to all day; and because they can now correlate data from their "omnipresent" WAF with the data from 1.1.1.1 they could get some interesting information... And believe you me, they're not sending it to /dev/null.