The best way to respond is with compassion and gratitude to the member who raised the criticism.
Thank them for their viewpoint and for caring. Provide the rationale for things you can’t change, provide updates on the things you can, and do everything in your power to build a bridge of understanding between you both.
You can ask for more information, solicit their input on what they would like to happen, and how. Maybe they even want to be involved in making that change happen?
This turns critics into friends and, maybe, friends into dedicated supporters.
Good community leaders are great at putting their gut emotional reaction aside and building these bridges of understanding. They know how valuable this criticism is.
The worst way to respond is to attack the person who raised the criticism, question their credibility, and attack their motives (worse still is do this in front of other members).
This not only risks creating a division within the community but turns members into enemies and shows to others that criticism isn’t tolerated here.
Criticism is incredibly valuable. Without criticism, you can’t have an authentic community. No-one wants to feel they can’t speak freely within a community.
One negative voice opens the door for others to express similar views and prevents a spiral of silence from forming. Criticism helps you stay close to what your members really want and not what you hope (or think) they want.
Personally attacking a member for voicing criticism is never the right approach.
Don’t reject criticism, seek it out, and welcome it. Validate it when it arrives and show members you want their views even especially when they are critical of you.