Yet, it's fairly reliable in most developed countries. So how will a developing country, well, develop, if it can't build a consistent, reliable power grid?

The rich countries should emulate China's Belt and Road initiative, but instead of building ports and highways they should build electric grids and renewables in developing nations. Ideally without predatory balloon financing that results in sticky situations down the line.

electric grid based on renewables require fossil fuels to be both made and as backup to be reliable. Electricity is not going to solve the 80% of the energy needs, its not going to allow them to do manufacturing and agriculture at large scale either. Its the wrong approach to turn developing nations into developed nations. I know most people dont like to hear it but that is the reality.

It being unreliable is a hinderance to it's development. Furthermore you cant't even do any of this without heavy use of fossil fuel.