The directory seems OK. In my case I don’t have the decluttering_templates directory, because I don’t use these templates. I also don’t have the views directory, because I didn’t install the examples. If you think you don’t use them you can delete these directories.
For the warnings, I have some too, but not as many as you. They probably come from the decluttering_templates and views directories.
On the other hand, this project doesn’t seem to be maintained by its owner anymore. It’s up to you if you want to invest a lot of time to add these cards.