The mane six let popularity and fame get into their heads

The mane six lost their purpose of spreading friendship in season 5-9 (after they got the castle)

They let fame and popularity and their ego go into their heads they have the tools (the cutie map and Twilight can teleport) to help out everyone but only helping out one side (ponies who friendship are about to break)because they have too big of a ego and think they're too important to help out ponies who are shy or introverted that aren't able to make friends due to being too socially awkward or too shy and they're all too blind (or egotistical) to see it because they themselves never struggled with that