Puppy won’t come back to us when called

My puppy (20 weeks old) has been struggling with coming when called when she’s off leash. She has a near perfect “come” at home with no distractions, and doesn’t pull on leash except when we pass by other dogs.

If we’re at the dog park, the only way we can get her is if she gets distracted by another dog or toy and then is tricked into being picked up. I know this isn’t ideal, but there’s no way to get her to listen, and she ignores treats when playing outside is much more fun.

I need help! We tried to use a long line leash, but she is fairly small, and trips over it or will chase/bite the leash. It also seems a bit impractical for the dog park as other dogs would get caught in it.

I think this issue is stemming from her entering the teenage phase as well. This is my partner and I’s first pet, and we live in an apartment in a city. When she was younger (14-18 weeks), we’d walk her every night to the park and let her off leash and she would run back and forth between us no problem. She understands grass = play, and not to run on the concrete. I fear we gave her too much independence and now we can’t get the boundary back. How can I retrain her properly? I think we seriously messed up.

This weekend, we were at my partner’s parents’ home in the suburbs. They live on a hill and their backyard is separated by a sloped driveway. She’s usually really good about boundaries, but she ran into the street and we were only able to get her when my partner’s dad knelt like he was going to play with her and then picked her up. I think again, this is a more fun distraction than us or treats, so she was willing to go to him.