Ellen Chisa wrote an excellent post about the real work, preparation, and skill that go into being a Product Manager at a tech company, and why it is disturbing when this work is portrayed as less difficult, "softer", or less important when women do it (as Chisa points out, when men do this work the role is often imagined as more masculine and evidence of CEO potential). In reality, as Chisa argues, Product Management requires a full array of both technical and management skills that are as important to product development as engineering, and thus Product Management should not be considered a stepping-stone or fallback role for people who haven't "made it" to engineering.
One thing I've noticed that makes the PM-shaming problem even thornier is that PM-shaming is endemic not just in external media representations, as Chisa notes, but among technical people, including product managers. This is to say that the first thing a PM often has to do is justify herself not as being an excellent PM in particular but as sufficiently technical. The assumption about PMs even from PMs is often that she is an "imposter until proven legitimate", where legitimacy means a convincing cocktail of technical background, product proof, career success, respect from engineers, etc. Unfortunately this reflexive policing-- are you a "real" PM or one of those soft ones-- replicates the same assumptions about "real/technical/valuable" employees and "fake/nontechnical/low-value" employees that have led PMs to feel their work is unfairly devalued or feminized in the first place.
As with all patriarchal problems, the problem of the devaluation of "feminine labor" (however "feminine" and "labor" are being defined at that particular moment-- as we know, even programming itself was originally defined as feminine labor until it became masculinized and valued more highly in the 1970s), won't end as long as that labor is considered less legitimate because of its association with the feminine.
Thus the solution to the problem of Product Management being seen as a lesser role given to people who couldn't cut it in engineering will be to undo the binary in tech between valuable technical skills and devalued other skills. Great products require both technical and cultural aptitude; however tech companies in their current form are organized to value and venerate the work on the farthest technical end of the spectrum, thus leaving PMs to fight for legitimacy and respect not just from the media but from their own teams and sometimes, from each other. This is why the Technical Imperative in tech-- where it is assumed that the more "technical" you are the more respect you are due-- is hurtful to everyone, not least because it keeps PMs continuously having to argue their own legitimacy when they could be building cool products.