There could be a few reasons.
- They don’t fulfil that idea very well. A French, British, Spanish and Russian Musketeer, Grenadier, Falconet etc. all look the same. It doesn’t really feel like you are playing one of those civilisations, it just feels like you are playing a generic European army.
- With every new civilisation the old ones feel less unique. The TWC and TAD civilisations are relatively immune to that because they already have a nearly 100% unique set of units.
- People just like new stuff more because they are used to older stuff.
Some relatively “easy” fix would be to add some visual uniqueness.
Give all Royal Guard units a unique skin. This wouldn’t affect gameplay but it would make Royal Guards feel more meaningful.
Imagine French Skirmishers actually looking like Voltigeurs.
Guard Musketeers already kinda look like Redcoats but I think they could also be made to look different for the British.
The Ottomans could benefit the most from that.
Replace all artillery crews with the new Great Bombard crew.
Give their Royal Guard Hussars and Grenadiers a more Oriental and not Occidental look.
It would generally be cool to just give all vanilla civilisations one new unique unit. That would make their armies look and feel more unique.
Like the British getting the Ranger now.