Actually, Wikipedia has similar issues to Google SEO spam, in the sense you now have people who pay marketing firms for articles to be written on themselves/their company. These articles, unsurprisingly, often infringe core policies like maintaining a neutral point of view.
With respect, I don't think the problem is as bad as you suggest. Some pretty awful articles have survived deletion processes so long as they are on a notable topic.
It's interesting how some Wikipedia articles are carefully fact checked and other articles at the same notability level were clearly written by PR hacks. I do my part when I find the latter. I remember going back and forth with someone from Theranos who tried to insert really promotional stuff into their article years ago. Guess I got the last laugh there.
With respect, I don't think the problem is as bad as you suggest. Some pretty awful articles have survived deletion processes so long as they are on a notable topic.