Without the kiss between Mera and Aquaman, her future is left as a whole lot more uncertain on the big screen.
All in all, losing the kiss between Mera and Arthur Curry probably doesn’t change a lot about the movie, although Mera actually loses quite a bit in the process of choosing Arthur over Orm.
After all, she was set to be queen, and after defying Orm and choosing Arthur, she is put on a very different path.