You don’t take puppies to dog parks because you have no control over the other dogs and dog owners there. You have no idea if the dogs are sick or vaccinated or socialized, and the last thing you want is your puppy getting sick with parvo or being attacked by another dog at such a critical age. Unfortunately not everyone knows the importance of this or cares about other people’s dogs, so dog parks can be risky even for adult dogs. I would definitely avoid it with a puppy.
You’re right that it is very important that your puppy meets as many different dogs and people and animals as possible, but you have to do it in a clean and controlled environment as much as possible. Try to meet up with family or friends who have healthy, vaccinated dogs. Enroll in group puppy classes or daycare or dog meet-ups where appropriate vaccines are required. Go on walks, bring your puppy near the park and practice training and playing there with the other dogs in view, so that your pup learns that they can be around other dogs without having to interact with them all the time and that’s okay. There are lots of things you can do, it just takes some preparation and planning. Socialization is a lot more complicated than just “meet other dogs”!