This is a poor video, in my opinion. It seems to be oriented around some concept of 'brightness' that doesn't seem well-defined by the presenter, and doesn't quite seem to correspond to any other commonly agreed-on definition of 'brightness'.
He gets off to a bad start by claiming that a major chord sounds brighter than a minor one because it has a major third in it. Well, guess what - a minor chord also has an interval of a major third in it too!
He also attempts to claim that a consonant sound comes from it having nether too much nor too little 'brightness' - totally ignoring all the other more standard reasons that things are heard as consonant.
The idea that different modes of the major scale have different levels of brightness does perhaps have some coherence, but that doesn't support the idea that going around the major keys arranged in the circle of fifths makes things "brighter" or "darker".
There is also some logic to the idea that playing chord progressions that go round the circle of fifths can make a piece sound like it's going 'down' or 'up', but the way it works is not because you're genuinely going from a 'brighter' place to a 'darker' place (or vice-versa), but because the successive chord motions are interpreted by the ear as going downward or upward. It's rather like this famous illusion:
Over a small range of movement, going round the circle of fifths 'sounds like' you're going down (or up). But ultimately, you get back to where you came from (hence... 'circle').