It's a special event for [fill in the blank] that the whole family wants to celebrate together, only Cameron and Mitchell are being nelly, Claire is being bossy, Phil lacks self-awareness, and Gloria is being tempestuous! Meanwhile, Manny has an impractical scheme that will unexpectedly unite everyone by the end.

That seems to be the plot whenever there's a holiday themed episode true but the writing is so clever that it doesn't get stale and besides it's normal for sitcoms to repeat themselves at times.

Gloria is so LOUD in every episode!

Annoying!:bash:

Gloria is so LOUD in every episode!

Annoying!:bash:
And so was Steve Urkel from Family Matters
Screech from Saved By The Bell
Jackee from 227

every sitcom will have at least one loud obnoxious character.

With Gloria its LOUD, LOUD, LOUD all the time. The other characters you mentioned were not nearly as egregious as she is in that respect.