Our efficiency in use of fossil fuels continue to improve.
Most plants produce energy at a range of 40 to 65 percent efficiency (the accepted engineering standard) compared to the theoretical maximum efficiency. Though improvements will likely be minor, it is realistic to seek a goal of 80 percent maximum theoretical long term. I do expect this to also flat line at some point in the future as efficiency nears closer to the maximum theoretical.
My problem with renewable energy production is due to the nature of the energy source (sunlight & wind is not as energy dense as coal) and the way it stores energy, we have already approached the point where improvements will be negligible. At this point it will have to be able to be mass produce and continue servicing these devices. That takes economical and environmental resources that could otherwise be going into expanding and maintaining our current nuclear energy infrastructure which produces more electricity today than all the "renewable" energies put together. Even when we haven't built a new nuclear facility since 1990 and have been heavily subsidizing every "green" program with taxpayer money nuclear is still the only realistic long-term strategy to resolve these issues. Though there will be safety and disposal concerns as well.
See the following page and article:
https://www.energy.gov/ne/articles/5-fast-facts-about-nuclear-energy
https://e360.yale.edu/features/why-...the-energy-solution-environmentalists-climate
But people are against nuclear energy so I guess until then I will support fossil fuels.