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(I know it was mostly a rhetorical question, but ...) It depends on where you are as a photographer. I'm absolutley of a mind that all people new to photography should be given a 50mm prime (or equivalent) and told to take photos with it.
But knowing that, there is an appropriate space for other lenses also. It also becomes a quality thing, when you know that a prime lens will cost 50% of a zoom lens and be significantly better in quality it is worth having the range covered that way
If you only had one lens, would you become a better or a worse photographer?