In Bitcoin, there is very little complexity at the base layer to determine how coins are spent.
True, although Script in Bitcoin is already very powerful. But it executes atomically which is the main point for me.
arbitrary contracts the ability to create and spend an unlimited number of assets on the base layer.
Agreed. The most insane part for me was that Ethereum Smart Contracts can literally run out of gas fees while running. Then there is an unfinished program execution on the blockchain for eternity. WTF. What kind of spam do these people want on their base layer? Nuts.