It seems to be mostly working for them, though I think companies that haven't gone so far down that rabbit hole are also doing fine. One of the premises of SRE that I occasionally take issue with is "build your own tools". That's a fine idea, sometimes, but it also results in NIH syndrome, which has a real cost.

Obviously, Google is operating at a scale that no one ever has before (and almost no one else does or ever will), and so, sometimes they have to invent the technologies for doing it. But, the somewhat dismissive tone of the SRE literature I've read that implies system administrators scale linearly while SREs scale drastically higher is kind of off-putting, and misrepresentative, I think. Sysadmins have been scaling systems for as long as there have been systems; sometimes just one person or a small team in the data center, running the whole show for quite large companies.

The opposite also occurs: a SysAdmin gets hired to do DevOps, but they're not qualified to be Software Engineers. The results is that, if you're not looking, your ops code ends up a series of "scripts" instead of a series of well structured tools.

But I guess this depends on the company culture to begin with.