Some interesting takes here.
I got to a local jam semi-regularly. In terms of the quality of players that show up, I'm somewhere in the middle of the pack. Not the best bassist there, but I hold my own with the better players when I get put up with them. There's a regular crew of pros who show up, and a regular crew of learners. I'm a pro, but not all that well known in the scene so I don't get the star slots.
However, that's not why I'm there. I find it funny that people are complaining about everyone wanting to show off but then also complaining about not being put into the spotlight positions. At jams, somebody has to play with the learners and beginners, and the point of a jam is to give people opportunities to play that they otherwise wouldn't have. I'm glad to do my time with those people 'cause somebody gave me that same opportunity when I was a bit more green than I am now.
There are people I go there with who are less experienced than I am who also mumble and complain about being grouped with people of equal skill. I'm not sure what the hosts are supposed to do, when their job is to organize an entertaining show and keep the people there as long as possible. If you put the loud, out of tune people up first, you're not going to sell a lot of beer. If you put the pros up first, you will get people dancing and they might stay until the end.
I think if you can't roll with the punches in the understanding that each jam situation is going to be unique, you probably should organize a private jam where you can play the whole time with people you know.