Wouldn't higher productivity also lead to higher profits? Which then should be taxed accordingly?
No. Corporate profits, especially when forwarded to shareholders, are very difficult to tax. Several companies that pay virtually zero income tax (apple, google, amazon) also now sit on piles of cash, piles so big they honestly do not know what to do with it. Thats where all the AI cash is comming from. They need somewhere to spend thier post-covid winnings.
Only if the increased earnings are treated as profits. Amazon famously had zero taxable profit for, what, decades?