I do not subscribe to PMM and I've only seen a few copies that a friend gave me, so I haven't observed their "evolution" over the years. But magazines only survive if they have advertisers, and advertisers only advertise in magazines they believe will deliver customers for their products. From what I have observed in our 2000+ boat marina, there are three basic categories of boaters.
Group 1 are the people with little money but a huge desire so they get whatever they can afford that floats and use it. Whatever resources they have to support their boating habit are tied up simply keeping their boat afloat and operating.
Group 2 is probably the largest. These are folks that have sufficent income to afford a decent boat in the 30-50 foot range, operate and maintain it, and upgrade it where it makes sense. But their primary focus is on keeping their boat in good shape, buying fuel, and so on.
Group 3 is the folks that have a lot of money to spend on boating. They can buy new boats or almost-new boats, and they can afford to outfit them with stabilizers, TracPhone and TracVision, $5,000 flat screen nav displays, $35,000 dinghies, and so on. Many of them have the time to take their boats on longer cruises where lots of boat toys can come in handy.
So if you are in the business of making marine "stuff," who do you think is your best market? Not Group 1. Maybe some people in Group 2. But everyone in Group 3 is a potential customer for your new nav system, new high-tech diesel engine, fancy dinghy lift, satelite phone system, newfangled stabilizers, expensive new miracle paint, etc.
So Group 3 is PMM's market today because Group 3 is the main market for the marine advertisers.
Those of us interested in reading about places we can afford to go, how to get practical use out of our boat, do-it-ourself projects to fix or fix up some aspect of our boats aren't going to find much of it in PMM magazine. In the PNW we have several inexpensive or free local publications that fill this need to some extent. I imagine the same sort of publications exist in other popular boatings regions.
PMM will still appeal to those people who can't afford to buy what's written about and advertised but are still intersted in all aspects of the boating scene. But to wish it will return to being a "relevant" publication for the average-Joe boater is fantasy I think. PMM has evolved right along with its market.