It's a pretty hard argument to work around: WebPKI certificates should go in the DNS, and also the largest DNS providers might at any moment decide not to validate DNSSEC anymore to get through an outage.
If there's going to be a single point of failure in front of your website, that single point of failure may as well be the only single point of failure instead of having two single points of failure, and it's probably important that people can't spoof responses.
Yes, it's a crappy outcome, but endpoints can still choose to enforce this. Further, it's not a persuasive argument against more DNSSEC usage, since if there was more DNSSEC usage then resolvers would be more reluctant to disable it.