How old is he?
I know my GSD pups don't tend to initially like to leave the yard period.
So I just use the yard for the general poops/pees. And for exercise, pack the pup in the car and go somewhere new.
How does he do when you put him in the car and drive somewhere for all your socialization trips? Why bother to 'socialize' and I want photos/videos of puppies/dogs.....