Islam is part of Somali culture and have been so for more than 1400 years. I don't see what you are getting at, there is no such thing as pure or static culture. You can't paint islam with the foreign brush because it is not. We accepted it out of our own choice as self determined people. Thus we made it our own.
Would you go to Tibet and tell them Buddhism is foreign Indian religion? Despite them having 1000 of years of buddhist history?
You can't divorce the complex relationship islam has and the role it played in shaping Somali history & culture.
Secondly Its ironic you lament over Somalis wearing jilbaab ,burkha and hijab calling it backward but is wearing jeans, t-shirts, hoodies, sweaters Somali culture? It shows how much you have a normalized western world view to consider western cultural clothing to be normal above all.
Somali culture is much more than dance, dish or dress, it is our beliefs, core values,family roles, manners, self-concepts, family values, social norms, concept of justice, rules of conduct etc.
It is our ''Ethos'' ..From Ancient Somalia til now respect for elders has remained an unbroken cornerstone in Somali cultural systems. Marriage rites, burial rites, ancestors rites, still honor their original foundation.
Somali culture is much more than aestitics symbols, rituals and language. its our virtues/ethos in otherwords our cultural laws.