Lazy writing? I don’t agree.
While it is all speculation on our parts, I believe Abrams planned to build Snoke up to play a larger role - but then Johnson suggested to undercut him (so to speak). The fact that Abrams did not insist on playing out Snoke´s arc only tells me that he wants to keep things unpredictable. But I would be very surprised if Snoke´s backstory were not mentioned in Episode IX.
As for Kirk´s death - yeah, it was definitely the role reversal that Abrams wanted. Still, Kirk could not stay dead. Just like original Spock could not.
Whether one finds the Genesis project in Star Trek II more believable as an explanation for having Spock return (and grow up so fast) in III - than the Tribble blood for Kirk´s survival in Star Trek Into Darkness… in the end, it´s all the same. Beloved characters most of the time survive and will be brought back from the dead. Which in itself is always, IMO, hard to believe. But I swallow the explanations in both films because - heck, it´s Star Trek, it´s space opera, and I want my heroes to live.
Would a much more elaborate explanation for Kirk to survive have been better? I doubt it. I actually am relieved that they did not concoct a much more complicated bending of scientific rules for that.
In other words: if the Tribble blood (in itself a fun nod) does not convince you, what would have?