Didn't Google announce thet they were ignoring domain age, unless it is an established site of course.
I haven't heard it but I think definition of "established site" is a bit different than most people know.
What makes a site established in technical point of view? Is it accessibility to search engine bots? What makes a site accessible? Is it to receive http 200 response by client? So, aged domain = a DNS (A record IP) that resolves for years and a homepage that gives http 200 response for years. Existence of content comes later than those 2 basics: working DNS and http server. Therefore content isn't required as long as homepage is accessible. It can be a blank page or a parked page with no real content. As long as it gives http 200 response it's an alive domain.
Dropped domains
Domains which have been not registered yet
Domains with nameserver-dns-hosting problems
are same, they are dead, unaccessible domains and pages. Http 404 error are similar but not same with the "server not found" error.
Therefore those "dead" pages should be excluded from SERP's immediately. Because end user of search engines would hate to click on search results if the page isn't accessible. It would harm search engine reliability.
Search engine bots visit the domain and its internal pages regularly
-first to check if the page is still accessible
-and then to check if the content is changed or deleted or if new content/new internal page is added. Search engine bots first check if the page is online. If the page is accessible, it's cached by search engines unless there is an exclusion in robots.txt or in metatags or in http header. So, if the homepage is accessible to search engine bots, technically its domain is deemed as an established site even if there is no content. So "established site" is a domain that's accessible, gives http 200 response to SE bots. It doesn't matter if it was a parked domain (with no real content) for years. That page has been always ready to get indexed and get ranked as soon as you add content. Because search engine bots visited that "aged" domain for years and it has been always accessible since years. Age is a trust factor because of this.