Didn't the price drop because the chinese started dumping their Doge? If that's the case the price will go up again when they re-enter the market. Doge is becoming a mainstream coin to be used everywhere, so there is a good use case. Bitcoin is also just a coin with no other functionality but that doesn't seem to be a problem. The statement that all cryptocoins need to fullfill some other purpose as well may be true for new coins but not for the old ones that have existed since the beginning.
IMO the bulk of the drop was mostly because of the Chinese exchange fiasco. Other than already being popular in East Asia, its the Chinese year of the Dog(e) in 2018 so a lot were holding anticipating a rise early next year, a lot of people dumped since the likelihood of a massive rise has been reduced - I still think there will be a rise at that time but the amount will likely be much less than if there was full Chinese confidence - I'm sure a lot will still be buying.