Impractical and stupid game design. for example there is veteran line infantry, regular line infantry, inexperienced line infantry etc etc etc instead of just militia + line infantry + ability to spend money on upgrading chevrons. Not to mention the fact that "unique" units like special regiments can be selected 4 (!) times instead of just one. This completely removes their special abilities, because they can be spammed.
The fact that the developers tried to be smart and used native names for each nation's units f.e. La garde de cheval for France instead of just horse guard. This game is in English, not in 5+ different languages.
Plenty of bugs like mute units (in NTW a unit shouted something when it was selected).
Unbalanced with stupid noob charges all over the place. If you don't put a reserve behind your lines then you will get noob-charged but if you do put reserves behind ur lines then your frontal line will get ass-raped by enemy muskets. So much for historical accuracy.
Also for some reason the world renowned Russian artillery has worse stats than French artillery + Russian artillery has higher numbers.. This is wrong. A Russian artillery unit should be cheaper and have same stats as a French one while having the same amount of guns. This is to compensate for the unrealistically bad Russian infantry.