What about drawing names, a sort of lottery. Everyone who wants to go signs up. If more people sign up than spots available, names are drawn. Yes, someone may not be able to go with their friend or "clique", but maybe that's a good thing. They'd be forced to get to know their fellow members. Or, they would possibly drop out because they couldn't go with their tribe and more spots would open.

Another suggestion, if you sign up for a retreat, you also have to sign up to volunteer for some type of guild activity or job for the following year. If you don't come through on said signup you can't do the retreat the following year.

I've been a paying member of various clubs and groups over the years and not been able to participate much and I've understood that you tend to get out what you put in and the less you are involved the lower you should set your expectations. That being said, I have a couple of thoughts.
It can be very overwhelming to join a group, church, club, guild and be presented with a list of expectations and the accompanying pressure to participate. (Example: visiting a church in my new neighbourhood and being asked before the end of coffee time after the very first service I attended to take on a not inconsiderable role in three areas of the organization (Sunday School, Youth Group and Choir!)). Another club's meeting was a parade of committee chairs all asking for "minimum participation" by each member of the club and then listing what meeting those expectations would look like. I have chosen to go elsewhere in some instances because of this. However, sometimes a dialogue has opened and I have found myself able to get involved at a level that works for me at the time and occasionally this has grown to my being able to take on a larger role later when circumstances were more favourable. My willingness to put the extra effort in later came because I didn't feel cornered at the beginning.
I think Peckish had the right idea - maybe engage with these members and explain the guild's expectations and needs and invite them to seek opportunities to get involved that work within their limitations/interests? :-)

One by One makes some points that are common experiences in every club, where it can be almost impossible to find folks who will fill executive positions and be effective volunteers.

I think it remains critical that guilds nevertheless remain inclusive and welcoming.

I did have one illuminating experience a few years ago: in the middle of a very interesting class, for some reason a few of the guild executive showed up and had a whispered conversation in the adjoining open kitchen...for about 20 minutes. This was typical of that guild at that time...there was definitely an "insider" group that ran things, but in a rather exclusive way.

This is the kind of thing that turns many quilters, especially newer and younger quilters, off guilds. Which is a shame. I look around our guild meetings and gosh most of us are over 70. We have to find ways to draw in the younger quilters and pass the torch!

YES! in order for out guild to retain it's "not for profit" status, our bylaws require attendance at at least 4 meetings (we do have several snow birds who are out of state for several months) as well as being on a committee AND submitting a charity quilt that meets our guidelines.

for some reason a few of the guild executive showed up and had a whispered conversation in the adjoining open kitchen...for about 20 minutes.

in my guild the board meetings are open to all members. We zoom so any member can attend from home. The link is in the newsletter email every month. Our board goes over the upcoming happenings for the guild and what is needed to be done to get it arranged, our treasury report if we need a fundraiser soon, etc. Nothing hidden or secret. Having a closed executive meeting is ridiculous for a guild and I would unjoined that very night.

Maybe go by seniority?

those that have been dues paying members the longest,: get offered the first chance to sign up - with a deposit.

If they pass on the first opportunity, they go to the end of the line.

This idea would, of course, have to be approved by the group.

Sometimes personal limitations (migraine headaches, mental fatigue) make it impossible to be reliable. Sometimes, the best we can do is show up occasionally.

What about having a retreat for newbies and wannabe members? Instead of limiting it to members, limit it to non-members, with members filling in the empty spaces. I would help to bring in new members, make new friends and an opportunity to teach and learn. Even the old, diehard quilters can learn a new thing or two.