Someone who has been in a role for years has often absorbed the issues and found ways to navigate around the biggest pain points (the upside of this is a deeper understanding of the environment). But someone who just joined can often see some issues more clearly than anyone else, and someone who is just finding their stride is in a sweet spot for delivering useful feedback.
I’m not claiming to know the ins/outs of classrooms, nor do I know enough about this person to pass judgement, but disdain seems rather misplaced and counterproductive.
Neither should all decisions about improving the system fall on newcomers, but they will have extremely important and valuable feedback. This seems like unnecessary gatekeeping if not tempered by reasonable policies that seek feedback from numerous sources, especially at a time when classrooms are in crisis and improvement is critical.
Blanket disdain is always a red flag.