Not exactly sure what led to your conclusion of a "worst experience" but honestly, the things are rather minor.

Re seating: Not the airline's fault if you couldn't do Online check-in. Seating reservation is on a first-come-first-served basis. Plus, didn't your family do Advance Seat Reservation (ASR), or was your booking class too low? With the odours and stuff, that's why the seats around the lavatories are not preferred. But if you didn't take it, then another person would've suffered.

Re delay: it's a fact of life. CX doesn't want this either since it drives up costs. I suppose they could've offered food vouchers, but since it was already 9PM (most people would've eaten by them), I think a midnight snack is appropriate.

Re heat: A known fact that Asian airlines prefer to turn up the heat to make the cabin more 'comfortable' (especially since the outside temperature in HKG around 7JAN was quite cold). You could always request the flight attendant to turn it down a bit.

Apart from the delay (which is actually quite common), everything else is fairly minor - not sure why it would be much worse than UA. If you were in a similar situation with UA (last row/next to lav, delay), I think you be even more disappointed taking into consideration the lack of PTVs on the HKG-SFO route. Delays with UA on HKG routes are actually more common than you think (due to mechanical issues).