I've been thinking about adopting a dog, but only if it's younger or a puppy.
Do you have a reason for only wanting to do adopt a younger dog?
I don't want to get a totally mature dog.
You should be willing to love all animals, even more mature ones, because they also need homes. With that said though, if you really want a younger dog then you should get one because you need to get a pet that you're willing to love or else you will just treat it poorly.
As long as the dog is cute, I don't really care.
Most mature dogs are just as adorable as puppies, but ultimately you should try to find a dog that's a good match for you so the transition into your home and life will be easy and you'll have a loving relationship with the pet. Dog's are long term commitments and you need to be able to love and support it for years to come.