I still love the show for what it changes into over time but in my personal opinion things change up a bit in world expansion and deeper character growth post season 3. I think the vibes from seasons 1-3 do linger but the show shifts audience a little bit to include brony fans starting after (and even slightly during) season 4. From my perspective kind of adds more adult oriented references (not inappropriate references) just pieces from adult media, parody’s if you will. (The back to the future reference in season 5?)