I think there are far more advantages than disadvantages of studying English alone. Internet does offer an incredible richness and diversity of tools for people who want to do self-study in English. Having uncountless English learning websites, excellent online dictionaries, newspapers, magazines, radios, books and videos at his disposal, the student can improve his English at the highest level. Yes, there’s a light at the end of the tunnel for those like me, want to study alone!
But none of these resources will work if the student doesn’t have MOTIVATION! Making an effective studying schedule certainly will take your English to the next level. You may study in the best English school, but if you don’t study hard at home you are throwing your money away. Therefore, Motivation is the key word!
In relation to the disadvantage of not developing communication skills, you really can boost up your speaking ability reading in aloud voice, listening articles or news on internet and after repeating everything comparing your pronunciation with the native speaker and correcting your mistakes listening again.(I did that when I was learning French because I didn’t have anyone to speak with…). The most important thing is to believe that you are able to learn English alone! So, let’s take the bull by the horns!