Saying that taste is just personal preference is a good way to prevent disputes. The trouble is, it’s not true. You feel this when you start to design things.
Whatever job people do, they naturally want to do better. Football players like to win games. CEOs like to increase earnings. It’s a matter of pride, and a real pleasure, to get better at your job. But if your job is to design things, and there is no such thing as beauty, then there is no way to get better at your job. If taste is just personal preference, then everyone’s is already perfect: you like whatever you like, and that’s it.