That is only true when the other language is one that someone else you want to talk to speaks AND the other person doesn't speak your language. Unfortunately there are thousands of different languages in the world, it doesn't matter what language you speak somebody exists who doesn't speak it and then you cannot communicate. Alternatively, if the other party has already invested in learning your language there is less benefit to learning theirs. (less is not zero)
Is any language a good choice? The world changes all the time, over my lifetime English has been the best choice for the majority of people - in part because the majority of language learners have chosen English making it self-reinforcing (which isn't to discount the other reasons to learn English). However history is not always a predictor of the future. Even if history is the best overall your particular future might make Kazakh the best language to learn. (I picked Kazakh because you have probably never even heard of it before)
Don't forget that time spent learning a language could be used for something else. Language is useful to know, but it isn't the only thing and you cannot possibly learn all the useful things there are to know. You have to choose and your choices will both open and close doors to your future. Good luck choosing.
Is any language a good choice? The world changes all the time, over my lifetime English has been the best choice for the majority of people - in part because the majority of language learners have chosen English making it self-reinforcing (which isn't to discount the other reasons to learn English). However history is not always a predictor of the future. Even if history is the best overall your particular future might make Kazakh the best language to learn. (I picked Kazakh because you have probably never even heard of it before)
Don't forget that time spent learning a language could be used for something else. Language is useful to know, but it isn't the only thing and you cannot possibly learn all the useful things there are to know. You have to choose and your choices will both open and close doors to your future. Good luck choosing.