I haven't yet. I think the gen 7 and get 5 Pokedexes are the only ones I haven't completed (though I suppose I technically obtained all of the gen 5 Pokemon in gen 6, as I completed the National Dex there).
There have been two issues for me. First, trying to complete a Pokedex that isn't actually the National Dex feels like a smaller and less meaningful achievement than what I've already done, and I've had trouble motivating myself to do it. Second, I've been feeling burnt out re: Pokedex completion, breeding, etc., all generation. I do plan to get back to the Alola Dex at some point, but I'm not sure when it's likely to happen.