JR, welcome. Wherever you read that, it simply isn't accurate. For a speaker to be "too bright" when being fed material which is well-produced with a flat response, the speaker would have to have a significantly elevated response over a broad area in the upper midrange/lower treble. Measurements show nothing of the sort and personal experience with good quality source material doesn't show it either. Speakers such as the Axioms which accurately reproduce what they've been fed will also reproduce the flaws in poor recordings. Using tone or equalization controls with such recordings can make them less objectionable.

Enjoy the music, not the equipment.