Yes, you read right. The leisure suit is still worn. In East Africa and Asia, it is still worn. Some parts of Mexico and Central America wear a highly modified version as well.
Like you I was completely surprised a few years ago when my brother returned with one. The novelty of it was quite nice and refreshing. Then the reality snuck in is it really wearable as a normal item. After questioning, he revealed everyone wears them back home and they come in a few varieties. He had a short sleeved version that is typical of young men; it is designed to be worn with an open collar, untucked, and with sandals or canvas shoes. The other two versions are both long sleeved with safari suit styling but much softer and less hard wearing cloth. They are worn untucked or tucked and have 4 to six pockets. The most popular colors for the cloth are navy, pale yellow, cream, oatmeal, brown, tan, white, and a red that fades into pink. Now the way they are worn is really interesting, it is treated like casual dress. While, the American would wear chinos, a golf shirt, and some loafers the East African would wear a leisure suit, a long sleeved version of coarse, with sandals or canvas shoes.
Is this wearable outside of East Africa; yes! The safari suit version in a khaki or cream looks just like a safari suit. Something everyone is familiar with. It definitely isn't as hard to wear as an ascot. If designed with tasteful details, really nothing '70s, it isn't that different. A shirt jacket with matching pants is all it is. I believe I've made my argument; me lord's I rest.
So, there you have it. An item written off by the Western sartorialists is accepted as a staple in other parts of the world. Dandyism is truly regional and that only adds to its beauty!