Large scale production of commodity goods is generally more efficient. Which is why microreactors don't seem to have any inherent disadvantages. The efficiencies tend to kick in with the raw number of items produced.
> microreactors don't seem to have any inherent disadvantages
They have diseconomies of scale. Some of the costs of a nuclear power plant scale sublinearly with power. Neutron economy is improved in a larger core. Larger turbines are more efficient than smaller turbines. It doesn't take 1000x as many operators to operate a NPP with 1000x the power output.
> microreactors don't seem to have any inherent disadvantages
They have diseconomies of scale. Some of the costs of a nuclear power plant scale sublinearly with power. Neutron economy is improved in a larger core. Larger turbines are more efficient than smaller turbines. It doesn't take 1000x as many operators to operate a NPP with 1000x the power output.