Why do I keep clashing with designers and how do I fix it?

Clashes with design usually are not about taste. They are about two people who care, talking past each other. You are pushing for the outcome you are responsible for. The designer is protecting work they have poured themselves into. When feedback sounds like a verdict on their worth, they dig in, and so do you. Neither of you is the problem. The conversation is. Design is a craft with reasons behind it, even when those reasons are not spoken aloud. Instead of saying what you would change, try asking what they were solving for. You will often find the choice you disliked was answering a real question you did not know they were holding. Once you understand the why, you can steer without stepping on the person. Before your next design review, swap out your opinions for the actual goal. Say what the work needs to achieve and who it is for, then let them bring the how. Give reactions as questions, not orders. You will get better work, and the person across from you will stop bracing for a fight.