Compressed images?

My son just sent me a wallpaper he found online and I received it blurry but on his end it’s perfectly clear. He sent me the link and I saved it just fine and so I sent the one I saved to him and same thing he received it blurry. We tried sending pictures we actually took ourselves and those arrive just fine. Seems to just be with images we save from online or screenshots. Both of our “low quality image mode” are turned off. We tried both on wifi and off of it just with cellular data and it made no difference. How can we keep them from compressing? The pictures we took ourselves show up as 1.4mb and arrive the same size yet for example the wallpaper we tried sending back and forth is being sent at 4.2mb but arrives at 229kb.

Both are identical iPhone 14 pro Max’s