When they do we tend to get ignorant choices (because 99% of them are not scientists or engineers) and corruption. A great example is our biofuels programs that gave us corn ethanol, which is literally the absolute worst possible biofuel for EROEI. Another example unrelated to energy is the Space Shuttle. NASA would have built a much more affordable and reusable orbiter had Congress not mandated a bunch of extra capabilities that were never used, specific contractor mandates, and other meddling that ruined the design.
Just tax fossil fuels and other carbon emitting activities. Do not allow politicians to get involved in picking the alternatives or they'll pick the wrong ones or be influenced by lobbyists for the most expensive or politically well connected ones.
I also don't like the categorical rejection of nuclear. I'm not strongly for expansion of current-generation nuclear power but I am also not at all opposed to more research on better ways of exploiting fission energy. I'm also strongly in support of increasing funding for fusion energy given the progress that's occurred in areas like compact superconductors and computer modeling. If we can solve fusion we'd at the very least have a source of base load power for regions with strong base load power demands and that lack large scale renewable resources sufficient to meet that demand.