This was not clear in your previous post. And I would say that you cannot assume that. I do not have any usage figures, but I doubt very much that TLS traffic is the majority - if even anything significant at all.
And I would argue that it still matters to do local validation. You assume that Quad9 (as well as any other DNS provider) is trustworthy and cannot be tempered with. We have already covered what people might or might not find trustworthy, but there is always a chance of infiltration or simply software malfunction. You are creating a single point that needs to be taken over and then many users will have compromised DNS.
Doing validation locally is way more expensive to break for an attacker if they want to compromise many users. Therefore this is no reason for me to disable local validation.