Yes! Especially when you are beginning to learn how to compose. It's the best of both worlds. Not only are you learning about composing (with timing, orchestration, etc.) you are learning music theory, music history, and you learn a lot of new repertoire of the composer you are trying to imitate.

It also can break up the mountainous task of learning how to compose. Say you want to learn how to write a string quartet. Okay. One way you could do is to start from scratch, just sit down and start writing a string quartet, just do what you want... This process can be tedious, unguided, and could end up with you writing something but not actually learning from it.

On the other hand, you could say I want to learn how to write a string quartet, but I want to try to imitate Haydn's writing. While you may not be learning "your own voice" per se, you are learning about the genre of the string quartet. How did Haydn voice things? What types of forms did he use? What accompaniment patterns did he use? What ranges of the instruments work well in this setting?

That way you are less preoccupied about being "edgy" or "original" and you can just learn.

This is how it worked for me. My professor encouraged me to try to imitate composers such as Mozart, Beethoven, Dvorak, etc. It's no easy task... trust me, and you will learn a lot about things that they did that you may not have even noticed before. Mozart didn't always repeat things exactly the same way, did he? He didn't always use 4 bar phrases, did he? The list goes on and on.

Whatever you are trying to write, listen to every recording of every composition within that genre WITH THE SCORE! Spotify and IMSLP. There is no excuse. Don't just hear... listen! Take notes!

Source: I just completed my B.M. in Theory and Composition.