1) not every employer will be able to succeed if they tried to object on religious grounds.
2) not every employer is going to even try.
What do you see as a common thread in the cases sent back for review by the orders to the lower courts in your own link? See anything? It pretty much jumps off the page.
Your other ruminations have already been considered and rulings delivered.
If they can justify & demonstrate their religious exemption, yes, employers should not be forced to violate their beliefs.