As far as I can remember from Metroid Fusion, the Metroid DNA is what allowed Samus to absorb X-parasites and reintigrate her old abilities from absorbing Core-Xs. When she absorbed the SA-X she "reabsorbed" her own DNA, that is to say that her original genetic condition is now complete with the addition of metroid DNA. I could be wrong, though. The game wasn't very clear as to what exactly happened. Perhaps Metroid 5 will clear this up?
Opinions are opinions, not facts. Though, everyone is entitled to their opinion, of course. Even Metroids and Ridley, the unkillable beast.
Viva Les Alpha et Omega Metroids.
Kraid should be brought back, he needs some good 'ol Metroid love.