First, on the presumption that yacht/boat club memberships are declining, I would first look to most clubs and yes even the Boy Scout membership is dwindling. The cause could be a social phenonium called the electronic age.
In the past people went out to do things, meet new people, make friends. Today, the phone is the ever present 'friend' to a lot of people. Which means you don't have to go out.
Second, snotty would imply that people wore ascots, jackets and even socks, but you won't find that very often today.
Third, according to Boat US, most boats on the water are 26' or smaller. Usually those owners, trailer there boats, from home to the water and back home again so they don't need a slip or mooring ball. Those would be 2 items that a boater might need to find membership in a club with like minded individuals.
That is the reason most join yacht/boat clubs. Sharing with like minded people who need slips or mooring balls. Someone who owns a 40' boat doesn't have a lot to share with someone who owns a 26' trailerable boat.
It was mentioned in a few of the posts I read, that they had acquired a mooring or a slip at a fee that was less than a local marina, and that can be the case in a lot of clubs. Less expensive drink and food prices can also be a reason, but not always.
Reciprocity is another reason. I attended a club last night after attending the Annapolis Sailboat show, we have a trawler, which wouldn't preclude membership, but we live in the Philly area and the boat was just left in Kentucky (we are on the Great Loop) and we like the Sailboat show as there are more vendors and not just sailing equipment.
The drinks at the club were what would be called 'market value', no reduced pricing, as were the meals. This club not long ago had made additions and acquired local land which was 'market priced' additions. They need to be paid for, by the membership. What those type of expenses do is help to maintain the club which attracts the members.
Often those who couldn't join a club or fraternity start by downplaying that association. There are yacht/boat clubs that are so exclusive, just like, BTW, golf clubs, that membership would cost way more than was acceptable to most of us and usually those membership cost would be considered a 'business expense'.
IF you would like to join a yacht/boat club, do as was suggested, call 1 and talk to the person who answers, relaying that you might like to join. They know you don't have to join and yes most are looking for members, so it will be like 'going on a date'. You'll look at them, they will look at you and if you both like what you see they will offer you a membership. IF you don't like what you see try another club.
You will probably find, if you invest the time, that there are others, where you would join who are a lot like you and that will make participating, yes, you will be asked to participate, more fun.
I'd suggest if you are married that you make sure your mate/partner would like to be involved as well. That is, of course, unless you want a place to escape to, to get away from, that individual.
BTW, a yacht/boat club is a nice place to entertain. I've even had Coast Guard Auxiliary functions at my club.
So, throw off the attitude, it won't go well if you try to join, and have a good time.