This is an interesting issue. My own thoughts are mostly dealing with the volume of advertizing that seems to have been on an ever increasing trend over the last thirty years. There always was a certain volume of advertising in the Model Engineer magazine it was however usually at the beginning and end of the magazine, then it began to move more and more into the spaces between articles.
I stopped the paper subscription because I felt that I didn't want to keep paying for more and more advertizing, it is for this same reason that I do not subscribe to electronic magazines it has become even easier for the advertizing to inundate the pages. I have a number of early volumes of model engineer leather bound these are the years 1972, 1973 and 1977, 1978, 1979, 1980, 1981 I still enjoy looking at them for various reasons. I do not have the sort of cash available these days to bind magazines, the ones I have are like real books.
The interesting thing about the advent of forums is the increased ability to share information especially pictures of methods or issues that can get a quick response by a builder who has had the same concern and solved it or found the answer to the concern and shares it. Also the ability of those doing similar work to share information, the forums seem like the perfect place to fill the spaces that were in the magazines that are now full of advertizing. I still prefer real books over electronic ones, the ability to put together a folder of relevant information though has become hundreds of times easier with the increase in participation in the world of forums. which are pretty much most of the time extremely pleasant, cooperative , civil and very encouraging. I would care to guess that there are more people these days attempting modelwork that they would not have dreamed of 40 years ago. Also the blending of disciplines seems more like the the very early days of Model Engineer mag where there would be an article about a steam engine followed by one about a marine issue then the serialized clock build. or the addition of a Myford gadget or nifty way to make a whatsit.
Enough rambling, just my take on the changing world of model mags and model engineering.
Michael