>>28216078You need to realize that these remakes are of the Ruby and Sapphire versions, not Emerald, which was the one who had the battle frontier.
Maybe this was a blatant way of showing us that the Battle Frontier was still under construction in the Ruby/Sapphire era and the Emerald version was actually set in a slightly later time where it was finally built.
Of course, this doesn't excuse their laziness, but you could argue them already having being involved in Sun/Moon's development and they didn't want to put all their efforts in the remakes. Making a Battle Frontier post game would require a lot of time and man work, which could have been proven necessary for Sun/Moon's development.
