If your product images are looking blurry / pixelated, most probably they're too small and stretched to a larger size.
WooCommerce has a new and easier way to resize the product images. You can change the WooCommerce Product Image Size in Appearance > Customize > WooCommerce > Product Images.
After publishing your changes, new image sizes will be generated automatically.
That should be it. After the process completes, you can go back to your gallery and refresh the page.