I kind of agree with what you're saying, I was so anxious to get a red death from a random drop but now that I easily just purchased it from xur I don't really care for it now. But on the other hand, maybe if there was a trading system or even a selling system where you can sell weapons or gear to other guardians then that would be a good idea. The way I see it is that if more people have better gear then it's easier completing raids and strikes instead of having one or more people holding you down. So IMO I'm ok with xur selling anything because it'll just help with raids and strikes when everyone has at least one great weapon and/or gear.