You're right that the vast majority do not speak arabic but there are plenty of people I've seen and debated personally that have advocated for it to be not only used as a language but as a first language as they believe it will make them more muslim, now i know it's just social media but you do have to wonder how many more harbor these thoughts and truly believe that not only is speaking just their language is more islamic, but dressing up like them and claiming to be from them/claiming to
be them. I see where this becomes a problem, this is just cultural evaporation, losing the entirety of your own or a majority of your own for another, then there are people who believe culture as a whole should be done away with, usually those who say that are salafis. Now speaking arabic will make it much easier to understand many aspects of our deen it being used as the only language that the people speak would in my opinion just create a big identity crisis.
Also in regards to their clothes i do not think we should copy them and instead revive the everyday use of our traditional clothes and even modify some to fit islamic standards of modesty, i see it as a much better alternative to the nitpicks of whatever arabs dumped at our shores and would in all instill cultural pride which is key to the strength of a people, uniqueness, i hate to call them out but I'd rather not want to see Somalia end up like Sudan