There is no density problem at all.
Fusion is estimated to be around 10 million times more efficient as classic fossil energy.
Basically it looks like this:
Fossil x1 million ~= nuclear fission x 10 ~= nuclear fusion x100 ~= matter/antimatter annihilation
You are correct with regard to energy production. Transfer, storage and consumption are where density becomes a problem.
Would you rather live in the stoneage?
Yes, I think the late bronze age would be a very fulfilling time to be a human being. I understand and accept that this is a personal aesthetic opinion, but I find it far preferable to the miasmatic dystopia I observe around me.
I mean with fusion energy abudant we will be able to colonize space and at least have an exit strategy in case our earth is destroyed.
in case?
Its nothing short of shear recklessness on the highest order to make reactors with a service life of a hundred years at the maximum, and to have materials power it with a half life of a hundred thousand years or more. The same narrative by the same entities over and over ad nausem driving this planet towards a toxic waste heap. It is a big ask to assume viable long term custodianship over many generations of such a hazardous technology.
Fossil fuels are actually incredibly inefficient due to the second law of thermodynamics. Even with a perfect Carnot cycle efficiency has a hard limit of 78%. Modern internal combustion heat engines typically are much less than this ideal cycle and can have up to 50% less efficiency on average.
We have a near perfect energy source just sitting overhead that produces more energy per second then the entire human race combined has used. Every square
meter of the upper atmosphere receives 1.367kWh of solar energy every hour, every day..year after year. It really seems dumb to me not to harness that for humanities benefit.
I desire to see the energy cartels disrupted as much as the banking cartels. Go environmental responsibility. Go solar. Go bitcoin.