Every event is gated somehow.
For most new events, it's by newly released characters who are either required or make the event much easier. For some events, it's an obscure faction that was of little relevance until now. For some it's gear on units you probably already have.
For this? They're going for breadth. And that is not an unreasonable gate. Particularly since that list has no bad units on it, and it's all stuff that's been pretty relevant for the theme of this six month block. The droids have been a super high profile team. 3PO and Padme are two of the best units in the game. GR ships are probably the next meta, and several of the pilots are clones, who are probably gonna be a big deal in LSTB. Shaak Troopers throws down at a meta level. Asajj is one of the best units in almost every game mode and has been ever since Mama T came to the game. And there's really only one panic farm in there. Shaak Ti. Every investment you make for this event will hold value. The most questionable is Mace for Endurance, but he's liable to get a rework and there will probably be an Endurance ship battle for LSTB.
It's quite the list, but nothing on there is unreasonable. I for one won't be getting there this time, but I'm certainly within strike distance for next time without going overboard. Most of the requirements were on my to do list anyways. Heck, several of them are on my arena team.