Since neither the general economy nor agriculture has gotten anywhere near getting off fossil fuels yet, that is assuming a lot isn’t it?
Even if electrical grid needs are 100% renewable, that is just a couple percent of most economies energy usage.
You're skating perilously close to "if something hasn't happened yet, it can't ever happen". This is not valid reasoning.
If the global economy can't get off fossil fuels, we're incredibly fucked, so I suggest there's nothing to be lost by assuming the problem is solvable.
For some places that is happening:
https://www.smithsonianmag.com/sponsored/more-than-98-percen...
2020 had the UK reaching 43%:
https://www.nationalgrid.com/stories/energy-explained/how-mu...
Interesting point about electric being only a small part of overall usage --- I guess direct heating and things such as smelting/refining metals makes up the bulk of energy usage?