GreyScholar

The problem is that the writers have completely underutilized Princess Celestia as a character, as of yet not having a single episode focused on her compared to the half a dozen episodes with Princess Luna

Princess Celestia has for all intents ruled Equestria for a 1000 years, in peace, by herself. As such logic alone would state as fact that she would be a phenomenal leader through experience alone, especially since if she wasn't there would be no sense in ponies adoring her so much. Also, with magic as something that can be learned and studied, improved as time goes on, reasons that she would be quite powerful. This is more driven home with how The Journal of the Two Sisters shows that she was a bookworm much like Twilight that liked learning, Celestia spending quite a bit of time with the father of magic Starswirl the Bearded himself and Luna saying her sister was the better fighter.

Also, it is in this books that one learns Celestia and Luna are born alicorns, along with how there was at some point other alicorns as well.

By all rights, Princess Celestia is supposed to be very competent and powerful, both as a ruler and an alicorn... yet the writers has failed to reflect this by continuing to ignored or neglect her in the narrative, without an episode to her name, will only make the problem worse.

Well, I will say Rarity is the sexiest unicorn in Ponyville... kidding. Rarity is drawn to be the most attractive character all around out of the main characters though it is possible that others can share just as an attractive design.

No, seriously!  You thought Spike was useless?  Try all five of Twilight's friends.  They might as well never exist in the show, and it wouldn't make much of a bucking difference, because they're that disposable!

I would very much argue against this idea, as the ONLY reason Twilight is wear she is today is because of her friends. If they had never existed, Nightmare Moon would have succeeded in taking over Equestria and making it Eternal Night. Discord would have been able to take over Equestria with ease, and Queen Chrysalis could have also taken over Equestria. King Sombra, well the Crystal Empire would have been his without resistance.

Equestria would have gone to Tartarus many times over if it wasn't for Twilight's friends nor would she have even become an alicorn princess. As such I don't believe you know what your talking about, or at least your view is tainted by bias and negativity.