I see. I'm quite unaware of this, so maybe you can fill me in. Is engineering knowledge something that would usually be published in a journal (paywall or no paywall)?
I just looked it up for my field (Electrical Engineering). IEEE is the go to association for publishing in the EE field. When I probed a little deeper, I saw that one needs a subscription to read any of the articles. You even need to be a member of IEEE before you can get a subscription. So essentially, pretty much everything is paywalled. Even the standards, which is ridiculous. It's like having to pay in order to read the law.
IEEE membership is hardly exclusive. I was a mechanical engineering major once upon a time, and they try to hit me up for membership every year. I could then buy any IEEE article I wanted to. I'm pretty much "just anybody" as far as the engineering community is concerned.
IEEE does more than just EE. Software engineering and aerospace engineering are also subjects they publish about. And they need members. Otherwise there won't be enough funding for them to continue existing I guess.