Thanks for reaching us; I'd like to inform you that just like other products, you can use Adobe Express for commercial purposes. That's primarily what Adobe Express is intended for.
The only factor would be the licensing terms of any stock assets you use in your design. The designs/shapes, as they are suggested, belong to Adobe. You need to modify the Adobe assets to create your very own work.
Please check these articles for more info:
Have fun creating with Adobe Express!