I actually find Google Flights pretty confusing. Haven't tried it recently though. Kayak works pretty well for me and I usually go to the airline's website to book directly when I find a good deal. If the price is the same I book via the airline website. For domestic flights I also check southwest.com since they don't work with Kayak and other travel sites.

Don't be surprised that many other travel sites cannot compete. After all, most of the sites are owned by either Expedia or Priceline. They are not startups. Also, they focus more on hotels since that's where the money is.