Evelynn is being changed because her stealth is binary and basic- you don't play around it, you don't interact with it, it's just... there. How many people even know it gives mana regen while she's stealthed? Plus her thematic is that of an assassin, which is high mobility and damage focused on taking out a single squishy target. But with no mobility besides a movement speed steroid, her low damage but high spam Q, and an ult that's an AoE damage and slow that encourages being used on high-health targets while they have lots of health, most of Evelynn's current kit screams "sustained damage diver". When people build her glass cannon, her ult is basically useless for anything more than a slow because she's too squishy for the shield to actually matter, and she wants to avoid the frontline whenever possible.
And all of this is before one even gets into her outdated visuals and model, short and shallow voice over, and utter lack of a concrete backstory and character. Evelynn is in fact much like Urgot was; she is indeed functional, but only just barely, and she lacks a concrete identity and thematic. She has for about as long if not longer than Urgot, and that's what the VGU is about: giving Evelynn a cohesive thematic that's reflected in her gameplay and ensures she brings something unique to the game.
For a similar offender, look at Pantheon. He's a man possessed by what is essentially a god who is looking to protect the last remains of the Targonian empire (and Valoran by extension) from an incoming threat. Yet his graphics and VO are generic homages to Sparta and Spartans, and his kit itself is shallow, uninteresting, and leaves little room for actual outplay potential on the part of Pantheon or his opponent beyond "proper use/reaction to the stun" and "proper use of/reaction to the ultimate". Evelynn is much the same in that she basically just runs you down. You either have the stats or the kit to beat her, or you die while trying to run away in vain.