about how voice training can result in loss of individuality and the qualities that made the voice interesting in the first place. The "homogenization" of voices resulting from certain training approaches is a common complaint in the opera world (there are a lot of bland, interchangeable voices out there).
But I don't think the problem is "too much" technique -- after all, many of the most technically skilled singers have retained their unique tonal qualities, and we can recognize their voices from just one note. Rather, I think it's a matter of poor or misguided training, or misapplied advice.
The issue of vibrato, which Annael mentions, is an interesting one, and widely misunderstood. Vibrato is not something that one learns to do; it is a natural property of the voice, which one can learn to either allow to happen or prevent from happening. I think many voice students don't understand this and try to force a vibrato, which inevitably sounds like a wobble, instead.