There is an old saying that I think still holds true: «A bad workman blames his tools». Good gear might make some things a little easier, bad gear might make some things a little more difficult. But good gear won’t turn a bad player into a good one, nor will bad gear hold a good player back that much.
Tell that to the carpenter with a warped and dull saw blade. A minimal amount of quality and specialization is often required for tools to perform the intended task. Sure you can cut angles with a regular saw, but perhaps a mitre saw would give better results.
Good players usually prefer an instrument with a good setup and specif feel and tonal qualities. Give them a bad instrument that doesn't fret right or produces a distinctly different tone and they will do their best to work around the instrument's idiosyncrasies. But if the instrument is bad enough, it will degrade the player's performance...or at least degrade the player's enjoyment of the experience.
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