The first counterargument always seems to be that at some point in future the energy consumption problem will be solved, but isn't the rate of computation a or the main factor against 50%+ attacks? Else the solutions proposed seemed to rely on centralized services that don't actually play on the blockchain to reduce the actual amount of transactions and load, also then avoiding the delays - but then re-adding the supposed main issue of having a "trustless" blockchain.
No his point is not about limitless energy or about off-chain transactions.
It is about a proof-of-stake scheme like ETH2 where the blockchain is still immutable, but due to a purely abstracted notion of "mining" which rather than electricity at all relies upon mechanisms where attempts to mutate the blockchain turn into pointless losses of money.
It is fully trustless, and I would argue even more trustless because it is accessible to all users, unlike mining.
No, there are other systems that work to solve the same trust issue such as Proof of Stake or Delegated Proof of Stake, as well as other variations on that theme.
The issue will be getting people to use something other than Bitcoin, not solving the technical challenge. Bitcoin mining will always be Proof of Work, and thus energy-intensive.
It's simple: democratically elected governments (save regulatory capture skewing policy to self-interests, continuing the status quo of directing policy to benefit certain individuals more than society as a whole) can create a blockchain with failsafes, without the Ponzi/MLM scheme/wealth transfer from later adopters to earlier adopters, and make it mandatory to use.
