The best available doesn't necessarily mean the best possible. And Google is far from it, and it's getting worse, not better.
Using a bit of Google-fu I'm usually able to find what I need quickly but it's still more of a hassle than it used to be.
It's easier to return the most relevant 10 results when there's only 10 thousand options than when there's 10 trillion options with 10 thousand new ones created every day.
My guess is that it's because Google Search now also has to cater to queries from Assistant. Being required to handle web, mobile, and assistant probably necessitated tradeoffs in quality of one over another.
More generally I feel like as the company gets bigger it just gets much harder to handle all the complexity and keep things focused.
First, I think search results at Google have gotten worse because people are not actually good at finding the best example of what they're looking for. People go with whatever query result exceeds some minimum threshold. This means when Google looks at what people "land on" (e.g. something like the last link of 5 they clicked from the search page, and then which they spend the most time on according to that page's Google Analytics or whatever), they aren't optimizing for what's best, they're optimizing for what is the minimum acceptable result. And so what's happening is years and years of cumulative "Well, I suppose that's good enough" culminating in a perceptible drop in search result quality overall.
Second, Google has clearly been giving greater weight to results that are more recent. You'd think this would improve the quality of the results which "survive the test of time" but again, Google isn't optimizing for "best" results, they're optimizing for "the result which sucks the least among the top 3-5 actual non-ad results people might manage to look at before they are satisfied". So this has the effect of crowding out older results which are actually better, but which don't get shown as much because newer results have temporal weight.
My warning is this, too, which you've surely noticed: Google search has created a "consciousness" of the internet, and in the 90s it used to be that digitizing something was kind of like "it'll be here forever" and for some reason people still today think putting something online gives it some kind of temporal longevity, which it absolutely does not have. I did a big research project at the end of the last decade, and I was looking for links specifically from the turn of the century. And even in 2009, they were incredibly hard to find, and suffered immensely from bitrot, with links not working, and leaning heavily on archive.org. Google has been and is amplifying this tremendously, by twiddling the knob to give more recent results a positive weight in search. Google makes a shitload of money from mass media content companies (e.g. Buzzfeed) and whatever other sources meet the minimum-acceptable-threshold for some query, versus linking to some old university or personal blog site which has no ads whatsoever. So the span of accessible knowledge has greatly shrunk over the last few years. Not only has the playing field of mass media and social media companies shrunk, but the older stuff isn't even accessible anymore. So we're being forced once more into a "television" kind of attention span, by Google, because of ads.
I know it's not google proper, but I'd guess a significant number of their searches are specific to youtube.