I'm aware the show has to end sometime. Heck, I was an advocate of ending the series like... three seasons ago.
Zim hits it pretty close. Specifically, I'm not buying the idea that Celestia and Luna are going to retire and leave a country's operations in the hooves of someone still young (and neurotic when stressed). Are the alicorn sisters still going to raise and lower the sun and moon after they leave the throne? Also, Luna has only returned from banishment for about... maybe 2 years? She's retiring already? As Zim said, this isn't anything that had a build up so it just doesn't feel right to me. Twilight as the princess of Friendship at least had a couple seasons building up to it. At present she has those duties AND is running a school. Gonna toss the crown of the country on her on top of all that? What time does she have for that?
Suddenly, hello now you get to be a bureaucrat! Cause that's what all little girls want after becoming a princess?