It does have a great impact. Nowadays TTL are pretty short because infra is very dynamic, you don't necessarily hit the cache that often. And a random webpage

It does have a great impact. Nowadays TTL are pretty short because infra is very dynamic, you don't necessarily hit the cache that often. And a random webpage will pull assests from all over the place, with many different domains/subdomains, all requiring DNS resolution. In the end, even if it's hidden you can definitely feel it in the "snapiness" of loading webpages. Of course when you only load/stream content it has no impact, so it is really dependent on your usage patterns. Running your own private DNS resolver is also much faster, even with a medium org, you can definitely feel it.