I completely agree. Pizza for a 2-3 hour domestic delay is appropriate. Pizza for 7 hours TPAC delay, especially when it's Delta's fault (mechanical) is absurd, especially for BE passengers. How does pizza hold anyone over for 7 hours when you're only going to get a slice or two?
Big fail on DL's part IMO, though I hope DL did right by you and gave substantial miles or e-cert voucher.