I don't think liveries give anyone 'desire', apart from a notable designer and his friendship group. If they were desirable by definition (as Andreos1 has pasted above), then we wouldn't have declining passenger numbers. Even pre-pandemic, I don't think there was any hard evidence that branding resulted in organic growth. On the most part, people used a 'desirable' branded bus, because they had no choice.

Much is made of Zap, Witchway or the 36 that Transdev run, but if you start using other parts of their network, its chalk and cheese in comparison. Burnley are still running some 22-year old B10BLEs in front-line service, which I'd suggest are about as desirable as a hole in the head to any non-enthusiast.

On the flipside, I think some of the innovations inside of a bus are more likely to encourage people to use them, e.g. comfortable seating and charging points, but it has to be part of a package. Fares and convenience are a much bigger part of that package, and on the most-part something that operators struggle to get right.