Canva is somewhat similar to bannersnack but does not allow you to create fully animated html5 banner ads. Instead, canva allows you to create more simple gif animations. The main issue you will run into when using Canva is that the file size of the gif animations you create will be larger than the recommended 100 - 150 KB file weight for display ads. This file weight issue is the main reason, advertisers have moved toward html5 animations which are able to pack Flash-like animation into very small file sizes. As for Flash, it is no longer an option for display ads since modern browsers no longer support the display of flash ads.
If you need help with design and development, VMR can definitely do it very quickly and effectively. Or we can provide banner design consulting to give you feedback and suggestions to improve your designs in accordance with your brand guidelines.