The problem here is not that 'good content' is not going to be found, it seems to be that in spaces where there is a ton of competition that the competitors are all in some kind of state where they all feel they and they alone have a right to be the ones to engage with the searchers on topic 'x'.
I highly doubt that in the use-case that you envision (which is indeed not one that I had in mind when reading the comment above) where you are providing to the point information about something you care about you'll find that your information gets drowned out by content that has been SEO'd to the hilt. But even if that were the case I'd blame the SEO guys, not the search engine.
Remember how altavista was spammed to death with on-page trickery and google came and it all suddenly was much better. At the time we did not realize that this would come at the price of the destruction of what made the web great, the links that would lead you from one place to another.
The fact that google is a monopoly is our collective problem, not google's, it's only a monopoly because we let them and because - for now - they are still the best way to get to relevant content.
The thing that could happen in your use-case is that someone would end up finding their information somewhere else or that they would engage with someone else. The only case where there would be a loss to them (your hypothetical visitor) is if they would not engage with anybody at all. But that can't really be true since we're theorizing here from the point of view where there is a glut of relevant content competing for a limited number of slots and then regardless of what the criteria are some of those sites will simply miss out on potential visitors.
The only real worry I have here is that the users would not find any relevant content or places to engage at all. And that's far from being proven.
Google does not have an obligation to the common good other than an ethical and a moral one, a real obligation is a legal one and I - in spite of being fairly harshly critical of google on lots of fronts - have no doubt that if they could solve the spam problem in an effective way would not need any prodding at all to go and do that immediately.
Demanding they do better is tantamount to dictating that an advance in technology be made, maybe the problem is harder than it seems?