Isn’t it funny the reason people criticize because deep down, they really care. If they didn’t care, why would they bother?
The same applies to your Brand.
There will always be customers who complain that the service is too slow, staff are not friendly, it’s over priced, etc. They criticize because they believe your brand can be better. They want you to succeed. They want you to be a better brand so they can engage with you. Perhaps fostering a positive relationship.
So don’t dismiss critics and complainers. If you can listen to them and address their concerns, you may be able to switch them to powerful advocates for your brand. A great story for them to tell their friends.