What size monitor are you looking at, and how far away do you sit? Those factors heavily impact if the difference is noticable or significant. The larger the screen and the closer you sit the more impactful the change is. Tvs are large, but you sit far away from them so they still look clear, for example.
On my desk I have a monitor arms with 2 27in monitors. One is 1080p and looks noticably blocky, the other is 1440p and massively smoother. Having used 4k 27in monitors in the last moving to 4k is a much smaller change than 1080p to 1440p at this size, although 4k is still noticably better, although if that jump is a worth the money is very subjective.