More people would be there because, like the Catholics or any of the others, you can do whatever you want without repercussions. You could attend a public talk without the disgrace or shunning. You could feel good about yourself.
I really doubt this very much even if they took away shunning their core doctrines would still be judgmental and negative. Maybe some people would show up once a month, or go to the memorial for family. Overall, though, active zealous members would go way down. They would have to change everything to be a place casual church goers would enjoy.