I remember that discussion, but I can't find it from satoshi's posts. Do you have the thread link?
It's here:
https://bitcointalk.org/index.php?topic=770.msg9074#msg9074To put it another way, who are we to change the way this thing works 11 years now? Shouldn't consensus change only if it's completely necessary?
Were P2SH
necessary? Was SegWit? Is Taproot? Even P2PKH isn't the original design, which was simply pay to pubkey. The whole point of bitcoin being free, open source, and decentralized, is that the community can decide to change things.
Not to mention that if we changed the protocol on that level, we'd instantly make every wallet out there useless.
Why? Taproot is a privacy improvement and will not affect existing wallets at all.