Doggos can be very excitable, especially when they are in a fun stimulating places with lots going on! The park for example, the park that the original poster describes in this thread is accessible to dogs, kids, and older folks trying to get their work out on, but they are strategically separated to avoid any overlap and potentially difficult situations.
Does Karen pay any attention to those very intentional separations? Why the heck would she. She is worried about herself and herself only. Karen is an entitled, self-centered kind of person, who wants her dog to become 'socialized' and thinks that the way to achieve this is to allow the dog to 'socialize' by jumping on kids and just being extremely poorly behaved. Not cool Karen. Thankfully OP acts as a thoughtful bystander in this situation and puts Karen in her place. All she had to do was keep the doggo on a leash to have better control over it! It's super important, especially in areas with a high density of little ones. Kids are often scared of excited doggos, it's just best to be thoughtful y'all. Think about others before yourself.