It depends. Lengths of articles would matter. Inches of advertising matter. Other things matter.
My initial supposition is that content today is not terribly different from 20 years ago. Having more articles, but on overlapping and similar topics, in the issues 20 years ago could be matched pretty closely content-wise by fewer but more concise articles today. For example, speaking on topics I actually can evaluate, the sports articles 20 years ago may have been more in number, but they covered the same sports with the same kinds of analyses, just by more people with more opinions. Similarly, the poker articles (more popular 12-15 years ago) could rotate the same kinds of topics and analyses among more authors, whereas the same content is basically covered by fewer authors today.
Another way to look at it is that having more articles 20 years ago meant that the content of, say, two issues would pretty much match the content of three issues today. Former issues from 20 years ago may have more going on in any given issue, but the overall Gaming Today content on an annual basis would be quite similar.
Also, since GT is a tourist tabloid for non-experts, it tends to run repetitive columns throughout the year on the same topics with similar, almost identical, information. Twenty years ago, it might have had three or four slot and vp articles for tourists in an issue; now it has two. The content of those articles will be repeated closely by other articles a month or six weeks out. The same stuff will be revisited. So really, the overall content isn't much changed by running the same or similar content less repetitively, which is what happens with a slimmed-down version.
As some readers have mentioned, Rob's columns fit the repetitive profile. They were anecdotal opinion columns with a great deal of overlap from column to column. If you took one of his columns from May of one year and compared it to a column from September of the next year, often you'd see an enormous amount of repeat information. That's to be expected; it's a tabloid for tourists.
So yes, reducing an issue by 50% or more wouldn't necessarily change content of topics covered and how they are covered. You'd just get fewer opinions on the same stuff, and instead of recycling info every six weeks, the same things would be repeated on a longer cycle today.