People only complain the length when it's delivered in a boring way.

You don't hear people complaining about the length of Xenoblades Chronicles for example.

You can never have enough of a good thing and the only problem now is that the actions we're doing in the game just aren't that fun.

I for one want to be able to progress in this game for years to come but at the same time I understand why people are complaining about this. Cutting the game shorter doesn't make it better. I'd rather see them addressing the problem with a better battle system more story content actually a LOT more and better made story content in all areas of the game.

Long story short. Don't stop working on the game and don't think cutting it shorter will distract from the fact that these people just don't care for a massive portion of your current product.