I'm going to be honest I honestly think Twilight has became very boring.
I agree. Dare I say it's her new found position as an administrator for a school that restricts her character from growing or being explored further. As a social standard her position requires her to be the living image of professionalism and as such writing interesting characteristics or adventures into her story is hard. Same goes for most of the mane 6 where their earlier season goals and problems have been solved either through their work or happenstance. The reason why Starlight Glimmer, Tixie, and even Cozy Glow come across as interesting to me is they are constantly struggling with something relatable or are hiding something devious; it makes them mysteriously interesting rather than "professionally predictable".
Continually on the other hand, Princess Celestia continues to be somewhat interesting though she is meant to be the ruler and maintain professionalism. There's clearly stuff she knows but doesn't tell anybody; it keeps who she really is just out of reach and thus a mystery. If you've read some of the comic books, Celestia's past with multi-dimensional mirrors is quite interesting in my opinion which in turn made King Sombra into a story hundreds of times more intriguing than what the animated show had time to reveal.
If you haven't already, I'd recommend reading the comics. For the last 2 years Humble Bundle offered a huge compilation of the series for $15; maybe they'll do it again when the show ends. When I become financially stable again I plan on buying the digital copies because they're quick enjoyable reads.