4K content on streaming is pretty terrible - so I can’t blame you for that opinion.

But comparing a 1080p Blu-ray to a 4K copy makes it a lot more noticeable, akin to watching a 480p DVD next to a 720p Blu-ray.

Lines are crisper, you can notice a lot more detail (skin texture on close-ups), background objects are clearer - nothing exactly revolutionary, but still an improvement nevertheless!