not necessarily in the actual war department
Which is a problem when you are talking about simulating war.
And this appears to have passed a lot of people here by, but, HOI4 does have a much more developed manpower and production system than previous editions of HOI. In terms of the economics of simulating WW1, I don't think it is at all obvious where it is less capable than Vicky.
In HOI4 I can produce artillery guns, tanks, aircraft, and infantry weapons of different marks - can you do that in Vicky? No. Instead there is only generic artillery and infantry weapons, and later tanks and aircraft.
In HOI4 I can intercept the enemy's trade routes with a distant blockade - can you do that in Vicky? No, you have to blockade specific ports. Submarine warfare is impossible.
In Vicky aircraft are simulated as a land unit. Pretty obviously this is deficient compared to HOI4.
In Vicky combat begins once the units arrive in an enemy province. This makes simulating trench warfare in a realistic fashion impossible - instead you have a war where your troops leave their trenches to attack only to find that their trenches have been occupied whilst they were attacking. By contrast HOI4 operates a much more realistic "move is attack" system where your troops only advance once the enemy has been defeated.
Vicky has no line-of-supply system for troops. In HOI4 this exists so you pretty much have to have a line of supply otherwise you will be defeated.
Vicky has a silly occupation system which allows you to advance through enemy territory without occupying it. Imagine a WW1 where the Russian march all the way to Berlin without occupying any territory, and then occupy Berlin. By contrast in HOI4 this is impossible.
None of this means you can't still have your generic wars-that-are-nothing-like-WW1 in Vicky. It just means that the real WW1 doesn't belong with Vicky unless Vicky changes a lot.