I think back before DAWs and home studios, you had to outsource the mixing and all the processes, you'd just come in with your band and your instrument and play the music.
Now I feel, if you do it yourself, you just get better and better with time. Not to say there isn't value in outsourcing it, but on some level, you're leaving something creative on the table, for someone who isn't you to do. That someone might be better than you at it, in general, and if you're really like new at it, someone else will be able to greatly improve the sound of things, but the more they do, the less you it becomes, I feel.
But similarly, the better you are at playing your instruments, the less mixing you need to do, creating clarity can be challenging in tracks with lots and lots of tracks and instruments.