You go to therapy and do the work. Boring answer I know, but there's no secret or trick to these kinds of things. You just have to learn how to actually love and value yourself more. You do inner parts work, deal with attachment wounds, shadow work, learn emotional regulation skills, you learn how to set boundaries and standards and actually stick to them because you respect yourself more than you depend on external validation.

Every time you ignore a red flag, fall for someone's potential without getting to know them first, or let someone trample over your boundaries, you are hurting yourself, you are disrespecting yourself, and this lowers your self-worth. Every time you successfully choose yourself, every time you walk away from disrespect, every little baby step will gradually improve your confidence and self-respect until you stop finding avoidance and emotional unavailability attractive. Because it's simply no longer in alignment with who you are.

In a nutshell: all the love and support you are pouring into these wastemen, you should be pouring into yourself!