I disagree. I am a layperson and I read both those journals regularly without much difficulty. Sure, some stuff is new, and you might have to look things up. It's not intended that everyone will read every article. You can rapidly figure out which are interesting to you - usually from the title, and if not that, from the abstract. Most of the time I will just skim a few key parts to get the main idea. Depending on how relevant or interesting it is to the question at hand, I'll dig deeper. Often it involves doing some work to learn something I didn't know before, but I consider that to be time well spent. I rarely spend much time on materials and methods. Most of the time I'm interested in results/discussion if the abstract is interesting, and if really interesting, the introduction can help give me context and a big picture.
Old copies are unread because no one reads physical journals anymore. Pretty soon there won't even be physical journals. Most medical professionals, if they want to consult the literature, will go right to pubmed and search for what they want. Relevance to a particular question at hand is usually more of a determinant of what one is reading than is the importance of the paper itself, although obviously doctors do need to stay on top of developments in their scope of practice.
There is a real value to precision in the written word (and spoken word) in science. Very subtle details can make a very big difference. We are talking about complex ideas. I don't think it's that professionals cannot understand them - I think it's just that complex ideas take time. The amount of information in the world today is growing exponentially. No one can know it all - or even know enough to make it easy to read any paper. It all depends on the level of understanding you need for your application. A surface understanding is usually very quick and easy, while a deep understanding requires motivation and effort.
People who don't really understand things do a lot of hand waving and speak in vague terms. (This includes me when I don't feel sufficiently motivated to look up the details of some pathway or mechanism, but remember the basic idea.) When you really understand it, you can use details. It is the reader's job to understand what details he/she does or does not need.
It's harder than it used to be for me to hold complex information in my head all at the same time - and it definitely requires more conscious effort, and I take more breaks. However, with sufficient persistence, time, and effort, it is still possible. I understand papers now better than when I got sick, because back then, I only had a rudimentary knowledge of the basic science. The more time you spend reading, the easier it gets.