So how do dogs ever get socialised
“Socialised” does not mean throwing your puppy in amongst a load of other dogs.
Puppies start off with only knowing other dogs - their mother and litter mates. Once it’s left the litter you become their family. You feed it, walk it, respect it, train it and socialise it - by firstly interaction with the pup, then introducing other people to interact with your pup. Once he has been fully innoculated you take him out to smell the different smells, hear children playing, traffic roaring past, walking on tarmac, gravel, grass, watch a stream running, watch leaves blowing, see other people walking, cyclists, joggers, kids playing and shrieking, allowing him to meet strangers other dogs - in a calm, safe manner. Ideally this will be dogs you know are friendly. You allow puppy to sniff the dog and vice versa and swiftly move on.
A puppy should learn the basics of recall before it goes outside of the home. You call him by name. Every time he responds you give him praise and a treat. This continues when he goes out. You take him to a large, safe area where there are no distractions and ideally, one person will hold puppy, you will walk a few steps, turn around and call him. He Will run to you. He will not run away. He only knows you. You mean everything to him. You are his world. Once he runs to you you praise him and treat him. EVERY TiME.
Socialising a dog is an ongoing process. As is training.
Find a good puppy class. They will give you the basics.
The biggest mistake new dog owners make when taking puppy out is to pick them up whenever they see a dog approaching. Puppy begins to believe other dogs are something to be scared of. Hence you end up with a dog who doesn’t like other dogs and is confined to a lifetime on lead.