My original thesis was that as the bitcoin prices goes up, transaction cost in terms of sats/vB goes down. 
In the year 2116, when the block rewards is 37sats/vB, I don’t think people will pay 100 sats/vB for fee.
And if you look at Saylor’s base case we will be at 13M$/btc. So maybe 1sats/vB.

With this thesis more people can afford UTXO than we are worried about. 

Second, i think shared UTXO will be a thing. Lightning is already a shared UTXO, albeit only 2. 

But overall it’s true, not all 8 billion people will be able to own a UTXO.