Solar is especially good at this, because with the right incentives you can have people put it on their roofs - it's the sort of scaling that's impossible to achieve in megaprojects like nuclear power plants.
That said, if you look at the total amount of energy consumed worldwide, the grow rate of this energy consumption, the amount currently generated by renewables, and the growth rate of renewables, it's pretty obvious that there's no realistic way to cut emissions 50% in a decade. Absolutely none short of a global war that devastates both modern society and reduces world population by 25%.
As you correctly point out, that's not going to cut it. However, there's an easy solution that has been suggested by various people for at least the past 50 years: Lower consumption, lower energy requirements, halt the desire for infinite growth.
US/EU energy consumption has been relatively flat despite population growth. The increase in energy consumption is largely in Asia.
Expecting these societies to limit themselves with your "easy solution" shows a lack of realism.
See also [1] for a counterpoint to your claims of increasing efficiency.
When you view Western energy consumption, it's growth is largely correlated to population increases.
However, that framing is de-emphasized in favor of politicizing the issue, imposing guilt on those who consume resources, and trying to alter the way billions of people live through coercion or decree.
We're screwed until the modern-day luddites yield that all of humanity wants, needs, deserves, and can sustain effectively endless economic growth and prosperity as long as the universe's limitless resources remain uncaptured. To think that at this junction we should consider the boundaries of human activity are now fixed is to just continue the endless tradition of doubters and cynics who have lacked imagination over the centuries, and held back all good things.