Most people here don't differentiate between mainstream and niche, it's just what smells best to them. However, current mainstream perfumery tends to be depressing (hospital cleaners, light woods and sugar for men, slutty pink syrups for women) and most old masterpieces have been reformulated beyond recognition. Niche perfumery is of variable quality, but one can find many great things. So we definitely need niche right now. But I agree that a lot of niche is as bad as the worst mainstream.
It is also interesting that some mainstream houses have created niche line to ride the fashion (eg Chanel exclusifs, Tom Ford private, Dior private, etc). Luckily, many of these are quite good.