Yes, it is primarily due to shrinking advertising share. When Google and Meta (Facebook) came along, they took the majority of ad money that previously would have gone to print magazines. That changed everything. I started out as an assistant (at Conde Nast) in 2004, and it was another world compared to what it is today. Budgets are a fraction of what they were, magazines are a fraction of the size they once were, staff at each magazine is probably half of what it used to be.
This x 100. Hence my support for the policy to break up the big tech (Elizabeth Warren had this plan during her presidential run) because one of the biggest problems from the monopolization of big tech companies is how they have ruined the media landscape. Print is no longer considered important because ads ran on magazines, newspapers, or tabloids don't necessarily result in measurable metrics (circulation and readership can only go so far) whereas digital can cater to marketing's full funnels with clear KPIs even down to conversion in which the return of investment (or ad spend) is more laser-focused, and when people are trying to actually purchase the product, the marketplace is also monopolized by Google, Meta, and Amazon's algorithm. This fast-paced shift to online-centric media ecosystem is what caused advertisers to be driven by the aforementioned platforms (Google and Meta, more specifically).
But nothing's gonna change anytime soon and such policy--although good--would be a wishful thinking because these big techs have policy-deciding politicians in a chokehold as well. It's a systematic issue that would position anyone against it in a losing battle which I'm afraid is where print stands at the moment. It may be an empty remark but print does need to offer something that online media can't provide (e.g going exclusive with contents, being so unapologetically glamorous with its fashion offerings for HF outlets that any influencers couldn't even dare try). However, with the lack of advertisers, can they even afford to go there?