I have met only a few people whose english is very fluent and good who havent traveled abroad, but I think it is rare. Even though, I agree it is not strictly necessary, traveling offers you much more than learning languages such as broadening your views of life and allowing you to try new things and have new experiences that you wouldnt be able if you stayed in your country. Therefore, I wouldnt substitute it for anything.

In my opinion, living for a good period of time in the country where you want to learn the language will always be the best and faster way to improve that language. If you think: there are no apps that allow you to be completely immersed in that language as you could be living abroad, where you are force to speak, listen, write in that language. Bye, Paulina