For me, it is the stage design. Stands out like a Stormtrooper among Space Marines.

Space opera is opera and so is Star Wars. Great music, great stage design, cheesy actors and a ridiculous libretto. Lucas can't write (but he can steal) and he can't direct (Harrison Ford is a very good actor, but not in Star Wars), but he had people that designed for him the X-Wing, the Stormtroopers and Yoda. Now there are others who just copy his formula: a mixture of samurai flick, Battle for Midway, Leni Riefenstahl and youtube kitten video.

The power of Leia Poppins.

Imbalance will sell more plastic via power creep, I am afraid. That is surely what GW is thinking.

This. Very concise and well argumented list.

If you want to have recognisable characters, smaller than 15 mm will be challenging.

Still an argument not to take vehicles. And you can influence the choice of objectives.

Vehicles still are generally a bad option. They can't take objectives. They don't have enough firepower to justify shooting at them. If you just shoot the infantry, the enemy firepower goes down with every trooper. So bringing antitank equipment is a bad option, too. There is so much of fake choice. Lots of options, but only a small fraction are viable. The problem with the AT-ST is not, that the sabre tank is better. Being a vehicle is the problem.