I'm not sure which engine option Scoot has but in the case of RR, most engines are leased to the operator. There will be a clause that stipulates that if the operator achieves an average derate of x or better then RR will refund them a portion of the lease cost. This provides an incentive for the operator to achieve derated takeoffs, hence it could be the reason for your "lethargic" takeoff. Also a balanced field takeoff will feel the same in any aircraft I would have thought.
The 787 is faster than the 777-300 and climbs higher.
On a 11 hour sector, with the same payload, one of our 789s burnt 20t less fuel than a 777-200er. So I'm guessing the airlines love it too.