This is an opinion that is only decidable by a person's tastes in music.
Plenty of amateur producers have become famous in Japan because of Vocaloid and only Vocaloid. Since most music is auto-tuned these days, aside from the lack of emotion and the fact unlike auto-tune they don't instantly snap into tune (leading them to on occasion need auto-tuning themselves), there is no difference between the real singers and Vocaloids at times.
Vocaloids are just a tool or instrument. Not everyone likes a guitar, some folks like bagpipes and others can't stand them. Everyone has preferences in music and many can't even tell when a real singer is off-key and out of tune.
Plus, not everyone can sing, therefore, Vocaloid is also here to fill the void.
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