The short answer is, Yes. If you don’t, the different strands will remain incoherent, insufficiently glued-together. The professionals do it, so if you want to sound professional, you’re going to have to do it. However, unless you know what you’re doing, it’s very easy to over-work in the compression stage.
Ultimately mix bus compression is finicky work, and it’s hard to discern the differences actually being made to the audio without a very sensitive ear and years of experience. But if you want your song really to feel like a song, and not just a mixture of mismatched parts, then mix bus compression is the only way forward. I wish you the best of luck, and don’t screw it up.