Doge Coin is a gimmick, the only lesson here is that there is still an opportunity for a new coin to gain a huge userbase fast.
Therefore; I still believe that the biggest threat for bitcoin is a new coin being launched by a collective of big companies who already have a huge userbase, infrastucture, marketing tools, capital, and most importantly, trust!
Such a new coin can potentially surpass bitcoin in market share quickly.
Remember, the average user doesn't care about decentralization or privacy, etc., they will use the most common and popular one.
The only way to avoid this potential threat for bitcoin is to gain mass adoption before such a coin is launched.
However; it is to be seen if such a 'collective big companies' coin will ever be launched, since it is probably more convenient for big companies to just implement bitcoin without to much effort.
In case of failure, it is only bitcoin that has failed and they can drop bitcoin again.
While as they implement their own coin, this will cost considearable more effort and dedication and will impact their reputation negatively in case of failure.
Financially doge is just as much of an gimmick as bitcoin. I'm talking about how much financial efficiency is gained from a legal company to adopt it's usage.
Doge exposed the face of bitcoin by showing just how important is the hype factor in the success of an crypto. It showed that cryptos don't have much to do with quality of the currency, but it's all about hype. That's why all the hate from the bitcoin cultists towards doge.
I think that this will change in the future, but right now, it's not hard to see why so many people see bitcoin more as an cult icon, not an serious financial tool.