Future proof image resolution?

What is the future proof image resolution for publishing online?
I uploaded all my images with around 800 px width, but viewed on a new 4K laptop screen it looks like this:
True, the page is not fully responsive, but still, 800 pixels is almost the minimum width even on a 5 columns layout, on a 4K screen.

Does this mean that to make it future proof, all the images should be uploaded with say, 2000 pixels width?

What should it look like? I can hardly see the images. I guess they are in green?
You can always auto size them or make them backgrounds using cover

image resolution is recommended to be kept to the minimum, cause this is where performance hits the most.