Flag design can be too minimalistic.

Indonesia is Poland distressed (and vice versa).

(See: <https://www.wikihow.com/Know-if-a-Union-Jack-Has-Been-Hung-U...> for general concept.)

There are near-identical flags as well, including Chad and Romania, Indonesia (again) and Morocco, New Zealand and Australia, Ireland and Cote d'Ivoire, Luxembourg and the Netherlands, Senegal and Mali, and clusters such as the Nordics (blue/red cross/field), Latin America (yellow, blue, red), and Slavic states (white, blue, and red).

<https://www.britannica.com/list/flags-that-look-alike>

There's the challenge between readily identified and readily distinguished.