You can be inappropriately vulnerable in front of people that you're not supposed to be vulnerable in. Being a leader that's vulnerable means in front of your team, but constantly going out on stage or in public and being vulnerable can often come across very insincere. If if you're vulnerable all the time, it might be because you're incompetent and making mistakes. So the problem isn't vulnerability at might be competence. But generally, no, you can't be too vulnerable. You just need to do it in the appropriate way.