Even big stars go on open auditions. It's open to them and to other big stars like them. You are not invited. Sometimes it may seem like this in the biz. What can you do to get the exposure and the experience that can bring you into contact with those kinds of roles? When will you find yourself going on open auditions for starring roles and substantial supporting roles?
Who knows the answers to these, and many other questions regarding open auditions? Maybe only the shadow knows. However, we can count on there being plenty of open auditions for you if that is your goal. The magic you see in the stars you admire is in you too. Even is you have to go on hundreds of open auditions it will be worth it if you are able to get that one great role.
The goal in searching for open auditions is not to find only the ones that will give you marquis status, but rather to increase the volume of open auditions that you go on. You never know where a small opportunity can take you.