Depends on what resolution you are watching the video in How good your WiFi or network signal is What the resolution video has been recorded in Are you using the YouTube app or third party app to watch YouTube with
There is some colour banding, but not so bad. Colour banding is subjective on the quality of the material being browsed. To make sure it's not a system problem, run a colour test and take it to an authorised phone shop to compare same image with other phones but be mindful of the display settings. Colour banding does not bother me so much on my phone as like I said, it's browser subjective.
It's called colour calibration and some older videos do not display correctly due to a number of reasons. The screen and display on the S24 and S25 series are calibrated to utilise a higher colour gamut than older devices. An unfortunate side effect is some SDR rendered content may appear off. This video is simply one of those cases. There's nothing technically wrong with your screen other than software.
