The way to get better is to mix. Everything and anything. To get good, don't just mix your favorite genre.... step out into unfamiliar turf.

Of course, if you rely on just the stuff you write and record, it might take a very long time.

However, there are sites online that have lots of songs in the form of stems. In other words, as individual tracks. You go there, find a project and download the tracks and mix it. Post it up on line for crits and feedback. Also.... of course, unless it includes PG tracks or other elements, it's kind of sketchy about posting it here. If you use a DAW, there's often a forum site for that DAW where you can post songs and projects for feedback. I used the Cakewalk Songs forum for that very purpose. There;s often a small cadre of highly skilled folks with good ears that can review your work and give you positive direction.

Use Google or your favorite search engine to get the names of the sites.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.