How to resize 2D sprites in the size of like 400px to 64px or 32px in a way that doesn't make it look pixelated and weird?
If you're using Photoshop, and you want resize a sprite, the best way to do it is by going to File -> Save for web.
And then play with this:
On Image Size, put the desired new width and height and play with the Quality, for resizing Pixel Art Sprites I suggest to use "Nearest neighbor". Once you input the desired size and quality you'll be able to preview the output and then save your image.