The use of Global classes is by Design.
we suggest creating a page where all your global class elements can live, like a Style guide page.
The benefit of this is that you are able to define all of your Global Classes which you can then apply to your design as you go.
There is a feature in Webflow to “Clean Up” styles. This deletes any unused style. The benefit of having the Style Guide page is that every global class is always in use, and you would never delete one of your Global Styles when you perform he Clean Up feature.