i would think that what is dull or meaningful is in the conception of the listener ,though aiming to please all comers may well limit what is done.if the session is a genuine singaround everyone gets as fair a turn as possible.at times someone more talented/well known appears and the organizer may give them much more time.this is their perogative of course as being the ones getting it together each week.
some of the open mics i frequent tend to do this as well and so i frequent them less in favour of the even handed ones.
its not something thats wrong or right,but its nice if there are other places that suit the contributers ethos better.