Earlier quoted context omitted.
But how does google find those domains? Link juice still matters, and those links work via... domains.
Those links work with domains or addresses no matter if it's https://yourdomain.com/ or https://[2001::1]/ . Google finds those domains through a variety of means (social media, collecting other domains from the sites they index, manually submitted domains, etc). Google also indexes addresses.
And you're similarly not likely to own an ip address forever, not to mention that if you have any doubts about the userfriendliness of domains, you don't need to wonder about ip-addresses. Ip addresses are worse on all fronts; leaving you back to square one: the DNS gatekeepers own your domain and merely let you use it. Just pray they don't change the terms of that deal.