From the post How do airlines handle uncertainty in passenger weight for weight and balance calculations?
[...] measurements need only to be "accurate enough" for the purpose of safety. Being off by small amount would not compromise safety.
For small planes:
[...] small enough aircraft, the actual weight of each passenger (plus luggage) must be used, rather than using a standard weight for estimation.
But, since your question focuses on aircraft performance, we find from the post How reliable is the Airbus FAC calculated gross-weight?
When the A320 is airborne, the [Flight Augmentation Computers] independently determine the aircraft gross weight (GW) by using the aircraft angle of attack sensors. If a significant difference occurs between the FAC and FMS gross weights (delta > 7 tons), the message "CHECK GW" will be displayed on the scratchpad.
That said, when an airliner's weight is in the hundreds of tons, we need to ask how much accuracy is needed? Accuracy to the 10 kg? 100 kg?
We see that the Airbus A320 becomes concerned when the delta exceeds 7,000 kg.
So, the answer is no, current estimations are more than enough for performance [and safety] for the big planes.