I ready about 30 papers weekly (below average) and I spend 2 days out of my week reading them. This without having to read anything, it would be a much worse situation where I have to read too many just to find that many of them are just written by cranks.
Someone can say we can can pay for people to have some sort of verified aggregate feed of articles. Yes that is possible and congratulations, you just reinvented peer-review system.
My strong guess is that your advisor was wrong (or you misunderstood him). I've often seen citations to random web sites. Even citations to conversations. The purpose of citation is to give credit, not rack up points.
Perhaps he was saying it was too risky to base your work off of some blog post, as his work was not yet "established" because it hadn't been published.
Even as a referee I would be happy with the former, provided that there is a permanent link or a pdf of the webpage in the supplementary material. I really would not let the latter fly.
I have seen exactly this. A (famous) professor at my university had a manuscript for a textbook that he had been working on for years, but had not yet published. A number of people wrote papers citing the (unpublished) book.
Of course, this is a bit of an outlier as the author had over the years given people drafts of his book.
Still, I would say that as long as the referee can access the web site and verify it, it should be allowed (and I'll still assert that it has been allowed on numerous occasions). May vary with discipline, though.