When you shut down in a relationship it automatically shuts your partner out. They will eventually start to pull back because they are feeling a disconnect from you. This can cause all sorts of uncertainties and insecurities between you as a couple if it is ignored for a long period.
You may also not realize that you are sabotaging your own happiness. If it is really easy for you to find fault with everyone on your dating apps or anyone you meet in general, you are creating an excuse to protect your heart from further wounds.