A couple of thoughts:
1. HOI4 is a sandbox game, and all nations basically have the same units, hence "Bismarck" or "88mm" are for flavour so the weapons aren't called things like "AT gun 1" or "Battleship 2". One nation's "AT gun 1" might be highly effective, while another nation's "AT gun 1" might be horribly flawed. So you're meant to spend XP points to modify each unit to your liking. If you want true-to-life 88mm guns, you spend XP accordingly.
I don't want to derail the thread with stuff I've written before, so I'll try to keep it short: I feel the problem lies in the variants designer itself, not in which flavour units were picked specifically for Germany. Some people suggested letting the player pick a design company for then to basically ask that company to produce, say, a Battleship with good engines and firepower. Then some time would pass and when the ship was fully researched, it would be roughly what the player asked for, give or take a couple points of stats. Then the AI could be scripted to lean towards historical stats, for example high speed and agility for the Japanese Zero fighter.
2. Naval combat and naval everything, for that matter, needs a rework, yes. I wouldn't call this a "German problem", though, and it's something they can throw into any patch or DLC.
3. I agree some models need work, the lack of jet fighters being the most obvious example.
