I literally cleaned my entire dryer myself last week and it still wouldn't dry out clothes without two or three cycles in the dryer. Thank God for the good grace of a kind dryer duct cleaner man that he came to my rescue and found the problem. I had a bird's nest in my dryer vent! I mean I'm bad but I know to clean the lint trap lol
That looked like a whole lot of lint, and some dog hair but dog was not the majority, in my opinion. I have a GSD so i have some experience with dog hair and dog fur.
Just crazy how it can even get this bad but nobody really ever knows or pays attention to their dryer. I just installed a new through the wall vent and my vent run is about 2 feet. Also don't like those cheap flex vents and vents that go to the roof.