We have never collected data on the flu or other respiratory diseases to this extent. The flu death numbers from the CDC each year a total guess, by their own admission. When an old person infected with the flu dies of heart failure or COPD, it isn't called "death from flu" on the stats. That concept is unique to COVID.
No doubt Delta is super transmissible, which is why it will burn out quickly and many millions of Americans have already caught it and recovered (if they even realized they had it). That includes many vaccinated people too!