Neither of those you named are Google problems.
Nobody of us might like spam, but there is obviously something that keeps these in the business. What? Eradicate that, remove their cash flow.
I might not like sites that aren't mobile friendly, but fortunately, when I'm not in a mood so scroll around it, I can always close it. No need for Google to step in.
I also do not like children being presented with porn/cigarette/alcohol/whatever advertising/results. But - these result do not come themselves, they are initiated, usually by those children. There is more need for parenting, than for Google protection. If it really bothers you, most routers allow for filtering the web, and some ISPs provide that as a service - for those interested, as it should be.
The problem with common sense vs censorship is: where you draw the line? That's the hard question, and easily abused one at that. Especially by entities like Google, who are not a harmless protector of innocent or knight in shiny armor. They are businesses, who have interest that may not align with yours, especially in the long run.