If something is not 100% fungible, it can still be fungible to some extent. Given the size of our electricity grids and to a lesser extent the capacity to store energy, electricity is definitely fungible at some level. I don’t have the numbers but I’d say this level is pretty high.

There are very few goods as fungible as electricity, even though it is not perfectly fungible.

If this were true we would not still be dependent on fossil fuels.

OP didn't say there were no goods as fungible, they said few. Fossil fuels can be more fungible without them being wrong.

Arguably, "fossil fuels" are not as fungible as electricity anyway. I can take electricity from any outlet and, with the right adapter, use it to power any electric appliance. I cannot take gasoline intended for my car and use it in a grill, or in the furnace, or in a jet, no matter what equipment I buy.

It’s the other way around. You can transport barrels of oil overseas and use for trading but sending electricity requires infrastructure that may take some time to deploy. It’s the same problem with gas pipelines.

How it is related? Fossil fuels are used primarily to generate and store electricity.

Even if electricity could be transmitted at any distance without loss we would use basically the same amount of fossil fuels.