For 99% of the people on this forum, this is probably a non-issue. Most of you are deeply familiar with all the units and enjoy the customization part. However for many new and casual players, the army-building part is intimidating. What units am I supposed to bring? What is a good army composition? How many chevrons, spells, items, mounts should I invest in? While Warhammer 2 does have an RNG button, they often create very bad builds.
This is called Decision Paralysis or Analysis paralysis. Where a person is given so many choices and options that it overwhelms and prevents them from making a decision and moving forward.
What I would like to see is for there to be a pre-built army for each race that are fairly easy to use, well rounded, and thematically appropriate. A new player looking to dip their toe into multiplayer could be handed one of these pre-built armies and jump right in. Or they could take that pre-built army and tinker with it a little bit to experiment with customization.
The units used would probably need to be constrained to base-game units because different people would have different combinations of DLC. However that should still allow for a fairly robust army. This would be a good opportunity for CA to solicit advice from some folks in the multiplayer community as they would know best how to build a well rounded army.
It's all about encouraging more people to get into multiplayer. The easier we can make that process, the more people will play.