wikihow is awful. Because it is burying useful content with their superfluous garbage.

OTOH StackOverflow employs similar tactics but it is legit and usually useful content.

Should Google discriminate between these two? If, yes based on what criteria? (Remember, wikihow pages look like they're user generated, legit content) Is there any objective criteria?

I personally would like wikihow to take its place in hell, ehm I mean obscurity. Right next to w3schools.