I think one should be careful of accepting either the 19th century morality of Mrs Bearne or that of l'abbe Barthelemy. Growing up at a convent was pretty standard for aristocratic young women at the time, it was only unusual for royal girls to go there - and it was done at the urging of Cardinal Fleury, to save the huge expense of keeping the individual households for what was a large family of girls for those days, not out of their father's indifference. The comparison with Madame de Maintenon is hardly valid - the comparison must be with Louis XIV, not a woman of modest birth who was charged with bringing up his bastards and later became his mistress, and later still, his wife. How could Louis XV be expected to model himself on her? Louis XIV was hardly a model of parental concern, and was demonstrably extremely selfish in his relationship even with his beloved Marie Adelaide, Louis XV's mother, insisting she travel when pregnant and causing her to have a miscarriage. While at Fontevrault the princesses were hardly neglected - their regime might have been misguided but it was not neglectful. (And by the way, Madame de Maintenon lost several of the royal bastards under her charge through illness - despite that anxious care). As for the court life of his daughters, it is difficult to see how it differed from the life of Marie Adelaide, or Louis XIV's daughters at their court debuts - and marriages at very early ages.
I think it is actually quite true that Louis XV was a selfish father, but for his times, not especially selfish compared to anyone else of his status and upbringing. Both Mrs Bearne and l'abbe Barthelemy were coming from the strong anti-Louis XV angle, discerning a decline in moral standards which would eventually lead to the serious problems of the French state (for l'abbe Barthelemy) and the revolution (for Mrs Bearne), which was epitomised by Louis XV's personal relationships - i.e., his purported indifference to his virtuous wife and children, and his greater affection for his mistresses. Essentially they were attempts to define the French royal family as a microcosm of the French state. All history is of course filtered through our own sensibilities, but I think we should be wary of filtering them through those of the 18th and 19th centuries.