Ships should have strengths and weaknesses. E.g.:- (Note, this is not how it is like in all cases, but in general; And isn't exactly how RM is, but how it is intended. And remember, range is a huge strength in this game).
+ (Positives)
KM:- Best Range, Best anti bomber AA, good number of scouts, good reload.
SN:- High Range, High Angle, Good damage
IJN:- Average Range, High Angle, overall best AA, best number of scouts.
US:- 2nd Best in Reload, Average Range, Average sized ships, Average damage, etc etc. Good AAW
RM:- Best Reload, Best Turning. Average Range
UK:- Best Submergence, Best DP, Average Damage, Ability to AW
MN:- Longest Range AA, Best Damage, Best Speed, slightly smaller sprite/hitbox.
- (Negatives)
KM:- Poor armour penetration, Low angles, worst salvo damage, Poor submergence and DP
SN:- Slowest Ships (Equal to UK AW), Slowest Turning, Long Reload
IJN:- Worst Submergence, Below average DP, Larger hitboxes
US:- No real weaknesses apart from Poor AA, and lack of a particular strength is one.
RM:- Below average damage, poor armour penetration, Poor AA, Low Angle.
UK:- Poor AA, Low Scout Number, Low Range, Joint slowest when armoured.
MN:- Low Range, Worst DP, Average Submergence
I've probably missed off a few things, as i'm tired and i've just woke up.
Some of these may change depending on ship setups and designs (e.g. Montana with level 100 guns).
There are some things you might not understand in there, but I will elaborate:-
DP Is ship Health
Submergence is sort of how much damage a ship takes. There are a number of guides on the ONF forums about this, it is called the AP Hull Cap (APHC).
Range is a huge strength and weakness.
Things tend to get tweaked if things don't work; Obviously RM needs a massive rework, but it will eventually get there (See the changes that are going on in the test server forum), and the game will benefit for it then.
However, unfortunately, we have to put up with it in its current state on release. Just as we did with Subs and SN.
