The time invested in practice should be worth the time invested.
Yet random yoga practice itself doesn't guarantee progress, it simply ingrains whatever patterns you are practicing.
If you practice a pose leaning a bit to the left, your body responds by leaning more to the left.
And the rest of the day you tend to lean to the left.
Practice doesn't make perfect, but it does make permanent.
Ingrained movement patterns are more obvious with a skill like piano playing. If a pianist practices the same piano mistake over and over, that mistake becomes ingrained in the sequence of notes they play.
Better musicians stop playing when they make a mistake, and work towards not repeating it again. They don't necessarily practice longer, they practice better.
In building a personal yoga practice, we look for methods of practicing better.
This practicing better is hard work, a brutal confrontation of the habits ingrained in both our body and our behavior.
We can't even SEE these habits in the beginning, our tendency to veer right when we think we are in the middle, the leaning of our head to one side as we sit at our desk.
Of course we can't see these things, if we could, we would have changed them long ago.
Yet how can we change habits we don't know we have? We must learn to see what we cannot and that starts with being a student of oneself, which gets easier with, you guessed it, practice.