I would say what you are seeing is more Etsy-fied than Canva. Search Canva templates in Etsy and that is where the canvas is muted and the same. For a couple of $$ they can get a bundle and just re-use. And any platform that provides free overloads the visuals. Think unsplash and Medium. Between that and copyright issues is why I use Canva daily.
There are large communities of people from artists, teachers, small businesses, and non- profits that use more than the social media templates and you wouldn't know its Canva. I have written hundreds of posts on Medium that I use my Canva designs on. They look nothing like the examples you provided.
I do understand your point of everything look the same, i get tired of it too, but its more about human nature than the company.