The biggest one I've run into is GDI support (Graphics Device Interface). This covers things like two-dimensional vector graphics, imaging, and typography. So simple things like transforming or drawing images are no longer supported.
There are decent third party open-source libaries like SixLabors/ImageSharp that have stared to fill the gap.
There are decent third party open-source libaries like SixLabors/ImageSharp that have stared to fill the gap.