Recently I purchase Nikon D5300, so first think I did is compare it with my 11 years old camera Olympus E510. Here are two test shoots with kit lenses at similar focal length. Nikon image size is reduce to match size of oly image. I need to mention that Oly lenses have fungi and Nikon lenses are new and clean.
So can anybody explain to my why older camera with fungi on glass make better photos than newer camera?
Also I have new Nikon AF-P DX Nikkor 10-20mm F4.5-5.6G VR lens that I tested in some landscape shoots and my first impression is that old Olympus have sharper photos with better colors. Nikon will probably have better dynamic range in same extreme situation, but it is possible that this is only on paper.
In dxmark website Nikon is best in everything when we look at budget cameras. I have impression that all that Nikon D5300 camera have digitally increased image size to 24 megapixels.
It is posible that problem is in cheap kit lenses, so I should spend few thousands of dollars on better lenses. If I knew that Nikon with kit lenses is so bad, I would buy used Sony A7 with kit lens, the real camera.
I'm complaining only about image quality, Nikon have more features like faster and better auto focus.
Not a camera body expert but your narrative suggests you realize that manufacturers will trade off certain features and emphasize those for a particular market. I use Canon and cannot see a massive difference between 600d and 80d except for more pixels, waterproofing and extra features. So far the features outweighed the expense. I understand that the rule is, the glass makes the difference not so much the body, so your theory on lenses may prove true.