This is a consistent issue with these sorts of CRPGs...reference Skyrim's "epic" battles between Imperials and Stormcloaks...oh maybe 20 people. Truly big scenes like we'd want are difficult to pull off, so I wouldn't personally put too high a priority on this.
I mean... ok... but then again Goblin Camp was a literal army with NPCs doing things everywhere.
If they can do that, they can pull the same thing off here and I don't think its fair to compare a 2011 Bethesda game to anything coming out in 2020.
Especially when its a Bethesda game.
