I'm not sure how Google handled the older HTML style websites.
The older HTML style Web sites are just that - static HTML. That basically means that Google can find them and index them just fine, which is to say Google finds them in the exact same ways it finds all the other Web sites on the Web. The two ways it finds them are 1) automatically with Web crawlers, or 2) you can submit your site to Google. In the case of Web crawlers, that means that some other Web site that Google already knows about has to have a link to your site. I don't know which of the two ways is the more common. I never submitted my personal Web site to Google, but I did share it with quite a few people. Somewhere along the way Google found it and has known about it ever since.
My Web site contains much more than genealogy. Indeed, my initial impetus for making my Web site was simply to store a vast number of "bookmarks" - sites that I visited regularly. I found that the bookmark support in browsers at the time was inadequate and that I was always losing my bookmarks anytime I went to a new machine or a new browser. Browsers are much smarter than that now, but I still think there is a fairly small limit on how many bookmarks a browser can manage in a truly practical manner.
RM's older HTML Web sites have been deprecated and my sense is that most RM users don't like them very much - too old fashioned and clunky. I don't expect to see them in RM8. But despite that, I think RM's older HTML Web sites have certain advantages over all of RM's new forms of Web sites. Namely, they are readily Web crawlable, there is no limit on their size, they can be hosted anywhere that can host Web sites, and there are no limitations or problems accessing them on your local disk in addition to accessing them on the Web. So if as expected they are not included in RM8, I shall be very curious to see what other alternatives for Web sites are supported by RM8.