Considering that fossil fuels "solve" the problem by literally dumping its waste onto the atmosphere, endangering the global ecosystem, and we're still merrily using them...

I think it's a bit melodramatic to say microreactors offload nasty environmental problem to the future. Also, their environmental problem is literally at the scale of "Drop them in an abandoned mine somewhere, where they cause zero harm to the world, and we will have a few centuries to figure it out."

Recapturing the CO2 from the environment of fossil fuels is almost impossible is almost impossible. Recapturing radionuclides is much much more difficult. Also the duration in which radionuclides are a problem has to be taken into consideration, making even babysitting nuclear waste extremely expensive.