I don't believe there is anything wrong or even questionable in Lightoller's survival
per se. As a human being, he had every right to save himself if he got the chance after Captain Smith gave the "Every Man for Himself" order. Lightoller left the ship after that order and took his chance when he got on board the overturned
Collapsible B along with others. Just like Ismay -
albeit under different personal circumstances - in saving himself Lightoller did not deprive anyone else of a place.
Having said that, I have mentioned my own personal opinion - and that only - that Lightoller subconsciously did not expect to go down with the ship. I am not saying that he had any specific plan in mind to save himself but IMO people like Lightoller and Lowe come across as those with a strong survival instinct. Nothing wrong in that; I suspect I have a similar instinct for survival myself.
What was really questionable were Lightoller's often vague, ambiguous and inconsistent statements during both official inquiries and thereafter, including in his biography. He gave the impression of being a good "company man" and making sure that he future career was not too adversely affected.