The first big events, The Elements of Harmony, The Grand Galloping Gala and the Return of Harmony focused on all six ponies. I admit that Twilight received more focus in some of these events (not Gala), but every pony still played a large enough roll and got her time.
The big events that followed were The Wedding, the Crystal Empire and Sombra, Magic Mystery Cure, Equestria Girls, Princess Twilight and Twilight's Kingdom. All of them seperate Twilight from the rest of the group early, presenting a story focused only on her. Be it wandering around in a daze caused by Twilight's errant magic or having to distract the other ponies until Twilight can save the day, the remaining mane six do little to contribute in the big events aside from a one-liner or two. Too many times, it is something "Only you, Twilight, can do."
You must travel through the mystic mirror. You must find the crystal heart. You must hide all our power and have a super saiyan fight with Tirek. Could her friends not have contributed to these events in some way?
I do not contest the point that Twilight is the leader of the group and always has been. But in the previous seasons, the show could be described as an ensemble cast. Since Season 2, that has ceased during all major events, instead favoring the formula of Twilight completely overshadowing the other cast members, to the point where their presence is no longer needed. It becomes Twilight and the Others, who busy themselves with trivial tasks until she can save the day.
Outside the premieres and finales, Twilight's level of prestige jumps around as need be. She absolutely is the talk of every foal in Ponyville and Rainbow Falls ponies are falling over themselves to buy her books, but god forbid she need a cab or want to visit her favorite author. Then she is reduced to as unimportant as any other pony. Put Celestia or Luna in either of those situations and see how absolutely ridiculous trying to selectively ignore her princesshood is. Back of the line, Celestia! The counterpoint to that is that Twilight must not be as important as the others, which is again ridiculous based on the amount of times she has saved Equestria.
I'm to the point of rambling about Twilight and no longer addressing your point now, but it's late so forgive me. The point I was hoping to establish is that even if Twilight was always the mane character, she didn't used to completely overshadow her friends every chance she got.