I think it’s puppyness, as well. I can’t understand why anyone would expect a dog of less than a year old to behave like a fully grown adult dog. Even the dog food bags say to feed the dog puppy food until they’re about a year and a half.
Think about a dog’s maturity in dog years, and compare that to human maturity. If a dog ages 7 human years to one dog year, then a one-year old dog has the equivalent of a human child’s 7-year-old maturity level. Would you leave a 7-year-old human child home alone for any amount of time? Probably not. (Hopefully, not.)
For a dog, at 2 years old, the dog has the equivalent of a 14-year-old’s maturity level. And while you might leave a 14-year-old human child alone all day, you might still place restrictions, depending on his or her maturity level.
My dog was crated until she was about 2 – she’s a Boston Terror and gnawed everything made of paper until about then. Our rescued Boston, who is about 6, still chews everything paper that he can get his teeth on. His development was arrested as a pup, and therefore I’m not sure he’ll ever learn to not chew (nor do I think he will ever be completely housebroken) but he’s a Special Case. (Rides the short bus to school and everything. I’m thinking of getting him a crash helmet for when the pecans drop from the tree in the backyard! He doesn’t seem to get, “Duck!”)
IANA vet or animal expert, excepting for the fact that I have four pets. I think the human to dog maturity ratio is merely a rule of thumb, but could be helpful in determining if it’s too soon to allow your dog to run free, crateless or not. Personally, especially since he’s one of those goofy-ass Goldens, I’d crate him until he’s about 18 months old and then experiment with short periods out while you’re away only. (When you’re home, he should always be out, with you.)
You could also work with him by having lots of chew toys around and replace the “bad” object with something he’s allowed to chew, whenever you catch him chewing. (This technique taught my dog to drop the newspaper in her mouth and run for her chewy toy as if to say, “See? I was being good. I was chewing on my chew toy the whole time.”)