"That's because you're not liquidating hundreds of million's years worth of accumulated fossil fuel in a century or two" This is variation of the "peak oil" fallacy which has been repeated since the '70's. The reason it is a fallacy is because it ignores the effects of technological innovation on supply. The recent shale revolution in the US is a perfect example of this. We have known about these deposits for decades but lacked the ability to access them. As some have claimed that we were running out of oil the quantity of proven global reserves have steadily increased decade after decade and will probably continue to do so for the next century, far after demand for hydrocarbons plummets due to the decreasing cost of solar.
The fair comparison of R&D budgets is on a per kilowatt hour. Of course solar has huge gains to efficiency because it is a new technology relative to hydrocarbons. Of course the R&D spent on solar is much less then hydrocarbons - because solar produces much less total energy (at this point) then hydrocarbons. The difference in absolute R&D investment is not a positive or negative for either energy source. It is simply a predictable disparity resulting from the difference in maturity of the two technologies.
The argument you should be making in support of solar is that solar panels are semiconductors and therefore are subject to something similar to Moore's law. While the output of solar panels are limited by theoretical limits, the cost of production is decreasing at an exponential rate and will continue to do so for the foreseeable future.
"The real problem is that renewable energy does not conform to a centralized model of concentrated wealth accumulation, so wealthy special interests are blowing a lot of smoke in your ears about it." This is a crackpot straw man argument meant to deflect attention away from the real problem. There are "wealthy special interests" advocating for hydrocarbons, but the same can be said to an equal or greater degree for renewables.
The real problem with solar is the Intermittency issue coupled with the storage issue. Intermittency can not be solved for solar. The sun simply does not shine at night. It does not matter how cheap solar power is, it will never be our primary source of power until we develop a cost effective grid storage solution. The good news is that the cost of solar power is directly related to the cost effectiveness (efficiency) requirements for storage solutions. If solar power costs the same as hydrocarbon power, then the cost of storage must be 0 or the storage must be 100% efficient. If the cost of solar is half that of hydrocarbons, then the cost of storage can be up to half or the efficiency must be
I believe that the exponentially decreasing cost of solar power combined with the slow linear decrease in cost of on grid energy storage will cross the threshold of hydrocarbon parity in the next 5-10 years and continue to improve afterward resulting in a rapid transition to solar, but it will not (and should not) happen before then. This has nothing to do with "conform to a centralized model of concentrated wealth accumulation" and everything to do with you getting the best price for reliable energy.