The issue I always see is the difference between the Mythos Elements and the Mythos Mindset. "We killed three shoggoths and a city of Deep Ones" isn't Lovecraftian. They're just inspiration for more powerful monsters, but they're still out there for the PC's to defeat, not to represent mind-shattering horrific beings which will ultimately crush humanity.
Classic Mythos is a doomsday scenario - at best you can stave off the inevitable. And much classic Lovecraft is not even about staving off the inevitable, but peeling back the onion to understand the universe - a universe where understanding leads inevitably to insanity. That kind of defeatist universe is not one many gamers want to game in, so the mythos gets twisted into something that can be battled successfully. That's still fun for a lot of gamers - but it's not really Lovecraft. His stories don't end with "and having sent Cthulhu back to the deep for another hundred years, the Captain retired, married, had many children and grandchildren and lived a life of peace and happiness".
Yeah his is how I see it. I know almost nothing about the Mythos. The little bit I do know I've gleaned from whatever influences have been put into Pathfinder and other material.
I also have a particular mindset about Horror.
If youre able to fight back against "horror" and possibly win? Then it's not horror, it's action suspense with some horrific elements in place.
If youre literally trying to survive knowing that eventually the horror is going to win or that you MIGHT be able to escape with your life and MAYBE your sanity intact? THAT'S horror.