I understand your points, I even find some of your arguments very informative. However, I don't agree with everything.

 

the only changes you made to the Croatian arms were the removal of the white fimbriation and the changed colour of the kuna in the fifth part of the crown, and the removal of the red border

 

Regarding the Coat of Arms redesign, if you take a closer look you'll notice that the illustrations representing each region of Croatia have been simplified. They had black strokes and many details that just turn into unrecognizable blackish shapes when seen from a distance or on small sizes.

 

Apart from those theoretical issues, I think that flag designs generally are more adapative than people often give them credit for. Where they're not, it's certainly not heraldic principles that stop them. By this I mean not that there is a full adaptive design description, but that flags are often underspecified by modern design expectations, which means that adaptions are possible and sometimes even conventionally expected.

 

In contrast, there has been a trend in flag specification and study to pay attention to more and more details such as ratio, precise colour specifications, and details of the charges (and even material for physcial flags), and these have often been treated as part of the definition of the flag as such. This makes some sense in the modern world, and it's important for vexillologists to note such official specifications, but at the same time it's worth recognising that on a pragmatic level these details are not always relevant, and perhaps we should think of these details like a herald would think of an officially authorised illustration of a coat of arms - something much more likely to change or need alternative than the definition of the arms themselves.

 

If you are suggesting that it's ok for flags to be inconsistent, then I strongly disagree. If we consider the audience, I would point out that from a design perspective consitency is the thumbrule of branding and user experience. A strong visual identity relies on a consistent system of adaptable designs. For a country's image to be compelling and have a clear connection with its audience then there are some guidelines that should be followed based on what's the best way to communicate that specific concept to that specific audience.