Upbeat moods can have as much weight and intensity as lower ones. IMO anyway, if you want to take them seriously, see them as being as important as any other emotion, and as a function of such consideration communicate them with writing and musicianship that excels. Not many care to. That happy songs can be done as well as any others just makes it more of a shame when they suck in the same ways over and over again.
On my own tastes, music written to cultivate any mood at all, high or low, is hard for me to stomach. The sense of emotional contagion as an artistic goal, that the writer wants me to feel a particular thing, repels me. I prefer to be presented with a story or an atmosphere that isn't full of obvious loaded words and affected crescendoes, toward which I might feel something different every time I listen. Not that it shouldn't have feeling. Absolutely not. The key word is have. Rather than creating a mood, a piece simply has a mood, while I have my own mood, and the experience is about the juxtaposition of and communication between our moods rather than their harmonization.