A critical spirit often comes from a place of idleness.
In my 30+ years of ministry, nearly every time I’ve seen a critical spirit tamed, God has used a change in station that altered their idleness – they got a job, they got married, they had kids, they started working on an education, they had a crisis, they started caring for others, they had a major move, etc. They no longer had the idle time to ponder the imperfections of others.
None of those things in and of themselves will cure a critical spirit. This only comes by the work of the Holy Spirit in conjunction with a follower of King Jesus who desires to walk in sworn allegiance to His person, in obedience to His Word, and in likeness of His character.
Being critical is simply a manifestation of our arrogance…thinking too highly or too low of ourselves. Humility is the act of thinking of ourselves less.
Humility cares for others…it doesn’t criticize them.
make my joy complete by being of the same mind, maintaining the same love, united in spirit, intent on one purpose.  Do nothing from selfishness or empty conceit, but with humility consider one another as more important than yourselves;  do not merely look out for your own personal interests, but also for the interests of others.  Have this attitude in yourselves which was also in Christ Jesus,  who, as He already existed in the form of God, did not consider equality with God something to be grasped,  but emptied Himself by taking the form of a bond-servant and being born in the likeness of men.  And being found in appearance as a man, He humbled Himself by becoming obedient to the point of death: death on a cross.