Those saturated images you're thinking of started as HDR but to display them on a non-HDR monitor they had to be converted first. The conversion process uses various tricks like local contrast to make it seem they're still HDR.

This can look quite natural when done right. But some people like to crank the settings in the converter to make the images super saturated.

HDR is high dynamic range. Basically, TVs that support HDR can show more unique brightness levels between the darkest and the brightest. That means you can have more contrast in an image.

I haven't seen an HDR TV in person, but I've heard people say that it's a more significant upgrade than the resolution jump from 1080p to 4k.

I have an OLED 4k from last year. It was a massive improvement over my first generation Samsung 4k tv. It's insane how dark blacks can get and likewise how bright the lights are right next to darks. Most people are used to black being a shade of gray. That's starting to be a thing of the past now.

HDR in monitors means (a) very high white point (800 to 1000 nits) and a very low black point. It lets you see more detail in the highs and lows. Its kind of replaced 3d as the new buzzword to sell super high-end monitors.

Speaking as someone who knows pixels, HDR is the first non buzz thing that's been out for a long time. Try it before making quick judgements