When working with 3D models the smoothness is defined by the polygon count. High resolution models will have smoother lines but the downside to that is that high resolution models also affect performance. In our 3D software iClone we do offer a Smooth Mesh option to help with the issue you but sadly this isn't available in CrazyTalk.
The only real solution is to create a 2D actor rather than a 3D actor in CrazyTalk. If you use a high resolution photo for your 2D actor you will get high quality output without the issue you show in your screenshot.