It is not time, it is money. And risk. Why spend 10's of billions extra (today's money) on the first full scale commercial reactor with the safer technology? And the risk of unforeseen issues? Instead take the lower risk and cheaper option to copy the military design. It is not technically implausible but economically implausible. It is like discussing whether some African colony could have been brought up to first world standards. Technically easy, implausible economics.
If it is so economically plausible, why are we still waiting for safe reactors two generations later? Easy, no one wants to eat the capital cost of the first few safer reactors.
A big problem with reactors designs using thorium as fuel is that uranium enrichment would not be needed or at least needed on a much smaller scale than OTL. The Uranium enrichment business is big money at the moment ...
As i said earlier, water reactors have the advantage of a very familiar technology ironed out by decades of experience with steam generating and steam using plant apparatus. HTGRs by comparison would require direct gas turbine cycles, something for which a lot less experience is available at the present time.