The ending of NEM was conclusive and a downer, but that's that. Characters killed should stay killed. That's reality and it really is important. Spock got a pass, not TSFS was great for it. Further what, is Data's katra supposed to be a computer virus that overruns B-4, leaving him a ghost program running in the background of his own body?
Spiner had issues with playing Data given how old he was looking. Data was supposed to be an ageless machine apparently, and looked much the same decades ahead in "All Good Things..." only with a dyed streak of gray in his hair. I can see why that was an issue for Spiner especially given that Data in the movies was more childlike than ever, and cheesy comic relief to boot - "flotation device" indeed. They did not have the character mature emotionally as he did in "All Good Things..."(!) so, yeah, I can see Spiner thinking a middle-aged man shouldn't be pretending he doesn't have jowls and playing in haystacks with children.