I don't think it's reasonable to ask the regulars to slow down for beginners, or to expect them to try to follow a player who can't play fluently enough to make the tune recognisable and keep it moving along steadily.

I wouldn't often slow down much, but I do quite frequently cope with the second one. It's one particular player who is never going to get any better - brain damage - but is very committed to the music. The tune comes out pretty wobbly but I can work out what it is, so I play along on a somewhat quieter instrument and pull the tempo into something steadier. Eventually other people catch on and join in, and the result can move from a shaky start to something that sounds pretty good.