You probably thought you didn’t “need” 1080p HD TV until you saw it for the first time—it’s the same deal with 4K and HDR.
4K isn’t the highest screen resolution you can get anymore (that would be 8K), but it’s pretty much the industry standard. Some prefer HDR (high dynamic range), which comes in HDR10+ (open) and Dolby Vision (proprietary) formats to 4K.
Most newer smart TVs and streaming devices accommodate all resolutions.