A rule that noise is okay at a park isn't as good as looking at the principles. Even in a park, time and place can be factors.
We met in a park with other families for years. Morning before lunch. LOTS of noise, sometimes staying longer, eating running, singing, rough-with-sand (if there weren't younger kids or kids who weren't with our group).
Keith and I also took our kids to parks after dark a few times, and swung them on swings to calm them down, and to have some fun in a cooler, quieter place after some big activity or other, or just for the fun of cold slides instead of the hot slides Albuquerque kids are used to. But we were helping them be quiet, snd screaming wouldn't have been good, in a residential neighborhood after dark. Yes, legally the park is open until 10:00 p.m. but "legal" isn't the only consideration.
Text (rearranged a bit) from SandraDodd.com/principles
photo by Kirby Dodd