I almost never saw it brought up, even in threads where people were defending ORAS. Why is everyone suddenly losing their shit over it being (very predictably) gone from Sun/Moon?

Its main useful feature was giving access to Hidden Abilities, but since their introduction every game had ways of getting that, there's no reason to believe that's gone,
Other than that, it had a nice interface but even if a DexNav-like feature returned that part would have been completely overhauled.