Having Picard, the Captain of the Enterprise, die instead of Data would have been a more profound moment.
Just before Data fired his phaser I was thinking wait they have that B4 prototype sitting back on the ship.
Yes, that's what everyone was thinking, I'm pretty sure. It was an easy way out. If Bret decides he wants to continue, he can always play B4.
This movie was clearly the end of the TNG legacy in feature films. It should have gone out with a bang. Legacies end when the leader dies in some form or fashion. The leader falls from grace, the leaders loses their hold on power, their leader dies, etc.
In the Trek universe, I think it should when the leader dies. Picard should have died.
Faced with the improbable yet confounding situation of having to kill one's self and knowing that this clone is all that's left of his family legacy, Picard should have taken the ultimate act of heroism and destroyed himself to destroy this corrupt copy.
In fact, a younger Picard would have done just that. It was uncharacteristic of Picard, IMO, to have that pause of indecision.