The biggest change is you can't rank in large highly-profitable buying keywords on the first page anymore without a HUGE budget. This is because Google has everything above the fold being either an ad, or one of the BIG boys like Amazon or Best Buy in many niches.
Used to be you could rank for something... a keyword like "buy window fan" on the first page with a good PBN, a targeted site, and some good authority posts. These days you'll find that keyword generates a strip of ads Google Shopping, two standard ads, a map showing you stores nearby (Walmart, etc) where you can buy it, and then organic results for Walmart, Home Depot, Best Buy, and Amazon... followed by another strip of Google Shopping ads, and more organic results for Amazon, eBay, and ONE site that appears to be an independent website like you used to see.
SEO in those gold mine keywords is DEAD. That's the truth. Today you need PPC for those keywords, combined with SEO for the (very) longtail non-buying keywords, and a lot of optimization and promotion on places outside Google (Reddit, Facebook, etc). SEO is not what it was.
-ThopHayt
