Or, what would you replace the self-destruct scene with, in terms of dramatic impact that the movie so desperately tried to achieve? Klingons kill not just David, but Saavik as well? Klingons kill Chekov (by accident, I presume)? Sarek dies before Spock is revived? Genesis revives not just Spock, but Khan as well?
Agreed. The sacrifice of the Enterprise
is possibly the most dramatic and memorable moment in the TSFS. It wouldn't want to lose it.