It's hardly a black and white area, and there's more to this question than just GOOG, but there's a joke here that has some relevance:

Those bastards have bled us dry with their algorithms, taken all the data we had, and not just from us, but from our children, our children's children, our children's children's children, our children's children's children's children... and what have they ever given us in return?

The search engine

...and a free phone OS

Oh yeah, the phone OS! Remember what the flip phones used to be like?

OK, but apart from the search engine and the phone OS...

Global Street View coverage!

Oh yes yes, oh that's a good one! So useful!

Chrome and Chromium

Well obviously that goes without saying: the browsers are very good

Docs and Sheets. I can't do me shopping without 'em!

Oh yes yes! -all nod-

OK, but apart from the search engine, the phone OS, the street view, the browsers, all the open source work, scholar, an office suite, an open DNS resolver, web fonts, gmail, and video calling, what has Google ever done for us?

> Oh yeah, the phone OS! Remember what the flip phones used to be like?

Mobile phones were always tracking bugs, but smartphones/Android made the surveillance much worse.

> Global Street View coverage!

At least in Germany still a quite controversial topic.

> Chrome and Chromium

By Google's aggressive advertising, it took an insane amount of market share of the much more privacy-focused Firefox web browser.

> Docs and Sheets.

Better use some offline-first office suite.

I like this, and I agree with the sentiment!

But does anyone else feel we might need to cross the search engine off this list soon? Since whatever happened which is reducing the usefulness of Google search (Search Engine Optimisation?), is search better now than it was in the pre-Google days?

Tangential question - would search engine optimisation have been less effective/destructive if there was more variety in the search engine people choose?

That's amusing, but it's another logical fallacy (non sequitur). :)

Was advertising necessary to produce all of this inarguably useful technology? Is this technology somehow unique in the world?

There are alternatives to all of those products that are not monetized via advertising. You may argue that they're not good enough, and I may agree to some extent, but they certainly work well enough for many people who decide to not use Google and other ad supported products and services.

Google et al don't have a monopoly on "amazing" technology. They just dominate the market to make it seem like they do.

Besides, it's not like Google developed these products in a vacuum (except perhaps early web search). Many of them are based on the work of other companies and individuals, which they either acquired, forked, or depend on. Which is fine, but the point is that not all of it is built and maintained entirely by G.[1]

[1]: The Roman analogy actually works in this sense as well, since accomplishments of the Roman empire were also largely based on work borrowed, adapted, or simply stolen from others. So were all the atrocities they committed necessary to advance technology? Perhaps. But if alternatives existed during their time that didn't come with the same downsides, I'm sure people would choose to use those instead, which is where your analogy falls flat. :)

I'm torn about this because I believe there's an amount of online services that should be truly free, for all, forever

For example, email. I use free emails since the 90s, never paid for it. I went long stretches having no disposable income at all - if I had to pay for email, I would have dropped it multiple times. However email is a postal box in the Internet - people don't stop sending you emails just because you decided that this month, a bag of rice is more valuable than an email subscription

(Nowadays email is like your online identity. People don't send you emails, instead, it's all services you use that send you access codes. Losing your email is truly scary)

On the other hand, I really loved the backup service of Colin Percival, tarsnap. It's an ultracapitalist, even libertarian, and it seemed to me very fair that you would pay for exactly what you use. If you stop paying he deletes your data, on the spot, no questions asked. (actually not sure if there's a grace period for permanent removal. but even if there is, this makes no difference for people that don't have money)

I had to stop paying due to life circumstances, I lost a backup.

I still have backups from around the same time in Google Drive, even without paying anything.

So really if we live under capitalism and such essential services like email and backup MUST be provided by private entities, then we really, really need ads and ad supported business that gives users permanent free stuff.

Fortunately capitalism can't and won't last forever. (but unfortunately it will surely outlast me and you)