Unless there are fundamental engine limitations on the number of entities in-game, which I doubt, that won't be true. You can normally throw lots more textures and lots more polygons onscreen and system requirements will rise, and you could do that to a degree that a game would be unplayable on current computers.
None of that is to say that this particular game will perform poorly. Just that a game being based on Unreal Engine 5 isn't alone enough information to say that it will perform well on current PCs.