So for the same or less power, you get more light.
How exactly is this bad...?
Isn't it the point to have everything well lit so you can see at night and reduce accidents?
You're right to point out the increased light is generally not done arbitrarily, but fulfills some purpose, such as reducing accidents.
The real point, in my opinion, is to have light where you need it, when you need it, not everywhere. Light pollution is a distinct but related topic, however. The shift to LED's was not intended to reduce light pollution, although there is potentially some opportunity to do so since LED luminaires can be more easily designed to control beam patterns, and can generally dim or turn off more easily than types like sodium vapor lamps when not needed.
As to the article, I'm going to just go ahead and be blunt and say Gizmodo wrote a badly misleading headline (the article is not as bad) that they should be ashamed of, on what appears to be relatively interesting research:
http://advances.sciencemag.org/content/3/11/e1701528
Issues:
1.) The primary reason for switching to LED's is to save energy, not reduce light pollution as the article seems to imply.
2.) A 2.2% annual increase in lighting over 4 years corresponding to widespread adoption of lighting that offers often in the ballpark of 20-80% energy savings versus the types of lights it replaces is not a "backfire."
3.) The study is not capable of measuring changes in indoor lighting.
4.) The study observed a *decrease* in the rate of lighting growth post 2012 compared pre-2012 (2.2% vs 3.5%). However, keep in mind my 3rd point, as well as be aware there were methodology differences that make the different studies difficult to compare.
5.) The study mentions another factor that is relevant - historically, humans have tended to spend about 0.7% of their money on lighting. Decreasing lighting cost spurring more demand is one relevant takeaway from that, but far more significant, I think, is growing economies in less developed nations.
6.) The brightest lit countries such as the US and parts of Europe tended to have little to no increase in brightness over the study period.
Keep in mind that global population growth is about 1.1% annually. That population growth almost certainly explains part of the increase, although probably not quite proportionately.
Couple that with the fact that most of the worlds less developed nations, which also tend to have the least lighting, also have the fastest economic growth rates (China 6.7%, India 7.1%, Indonesia 5.0% vs United States 1.6%, all inflation adjusted), and there should be an expectation that a lot of countries are becoming increasingly able to afford to install lights in places we were lighting up decades ago in the US. The three countries I mentioned above alone account for 40% of the world's population, by the way, all rapidly growing.