I agree with the others that this new building requirement system feels a bit off.
I do appreciate the system of "higher levels of units have longer production times, unless you construct higher levels of the appropriate building". It adds more meaning to higher levels of units, more than a mere stat improvement.
However, it feels really off, mostly because I am used to CoW 1, CoN, S1914, that all units are produced so quickly using lv1 requirements:
A destroyer and a battleship both have the same requirement: harbor lv1. In 30 minutes you can contruct all building requirements for the entire navy. Somehow, you don't need an improved dockyard to construct gigantic battleships.
The production time is very interesting as well, 4-11h for a battleship? Lets compare it: S1914: 3 days; CoW 1.0: 2d16hrs; CoN: 1d6hrs; Hoi4: 1yr minimum; reallife: 4-6years.
Battleships should feel like a huge project, not something built in 4-11hrs. Though this maybe something we have to get used to, since all units get produced so quickly.
Most importantly, there is no economic trade off to go for battleships. In CoW 1.0, the deicision to go for battleships is very significant: Do I really want to commit to a lv3 harbor and let the world know I am producing battleships/carriers? A lv3 harbor takes 4d total to construct, do I have that much time to commit? How many production centres for battleships can I afford? In how many cities can I afford to produce battleships non stop? Am I aware that the earliest I can get battleships is by day 6?
In CoW 1.5 there is no such decision. The decision to go for battleships, or other "supposedly expensive / non-early" naval units is made more easily. Economically speaking, the difference between battleships and destroyers is merely the increased cost in the production itself. There is no difference in the cost of building requirements. You don't think of battleships as "early game" unit, yet they are, you can get them in day 2 already because the building requirements are almost non-existant.
This is only an example for naval units that is translatable for others such as interceptors <-> strategic bombers.
"Hey, why don't I start harassing my neighbours cities with strategic bombers on day 1!"
You can get an interceptor produced earliest: research 2h30min + production 2h45min = 5h15min
Anti Air: research 30min + production 2h45min = 3h15min
Strategic bomber: research 5h+ production 3h15min = 8h15min.
At least you can get interceptors or anti air before the enemy gets strategic bombers, but lets be real, who goes for anti air/interceptors first? When you see the enemy build a lv1 airfield, do you think of strategic bombers? Unlikely.
Can you imagine getting your cities bombed on day 1? Your buildings destroyed from air by day 1? You have barely finished the 2nd round of light tank production when strategic bombers are raining death from above. The city morale didn't even have time to change from 70%. Your spies didn't even get to work yet to see if there are any speical threats from your enemies to be concerned about.
On the other hand, why even bother disrupting the production of the enemy? You destroyed my tank factory? Jokes on you, in 30mins I got a new tank factory and can resume production. The strategic bombers probably didn't even return to their airfields for refuel when my tank factory already resumed production. I need to stop you from producing carriers? Unlucky because the building requirements of a battleship are fairly cheap and built in 30 mins. Even further levels of naval dockyards are constructed rather fast. Can you imagine flying 15 strategic bombers on an enemy harbor, completely destroying it, grounding an entire city, while having disrupted the carrier production for a mere 30mins before the production is resumed?
You want to use military sabotage spies to stop my carriers from being produced? Tough luck because I can produce 5 carriers minimum between each spy action. Even if you disrupt my carrier production, you invested so much money into the spies. 15.000$ per spy one time cost, 4.000$ per day change. I won't even bother placing counter espionage spies in my carrier production city. Reparing my dockyards is probably cheaper (and faster) than your usage of spies. Once every 24 hours you disrupt my carrier production for 30 minutes. Absolutely worth it!
Reduced time in production and construction feels really weird. I am playing a mixture of 4x speed and 1x speed. During the time I need to conquer a rather large province, I can produce a new unit. My spies have uncovered the entire enemy army? By the next day change my enemy might have an entirely different army because he produced so much so fast. I scouted his homeland with airplanes, determined its empty, launch a surprise invasion with light tanks spear head, by the time they reach a city, the enemy already produced anti tanks. The enemy didn't even need the building requirement beforehand, it is construced in 30mins anyways.
Lets say Germany is conquering Poland, his armies are on the gates of Warsaw. I, France, decide to attack Germany because he is distracted. Germany has very few units at my border. I attack. Germans manage to buy quite a few hours because of homeland bonus and a fortress. I breakthrough but I see the German army advancing into Russia, ignoring me? No. Germany built an entire new army. Why bother taking the German army from Warsaw to France when you can produce a new army, faster than the old army can arrive from the east. The time it takes me to reach Berlin is more than enough for Germany to produce half a dozen of units. (This is a drastic example based on theory crafting, might be a bit overexaggerated)
If its hard to imagine, imagine this: In CoW 1.0 you reduce all unit production times by a lot, so that units only take 2-4hrs to produce. You also cut the building requirements to level 1, and their construction time to 30minutes. Imagine what kind of chaos it would be.
Here is an example from my curret map:

I want to shell the enemy position. I want to use artillery to attack the province Schachty. I have an artillery production in KRASNODAR, my artillery in this picture still needs 5h until it is in range. You know what is faster? Construct the appropriate building and produce a new artillery in ROSTOW. This is even a tiny distance. Can you imagine this for larger countries? Why even bother constructing units in the backyard, by the time these units arrive at the frontline, the frontline cities already produced multiple.