What does Canva do well? They make templates that are extremely easy for an amateur designer to create high quality work in a very short period of time.
What does Canva not do well? When you export files from canva you have to pay extra to get the actual file (a jpeg is not a file), you also have to pay for some images and visuals on top of the subscription fee. You spend so much time designing it but then not being able to have the illustrator file without paying more.
What do you wish you had known about Canva before using? That it costs additional money on top of the subscription, such as exporting files or selecting some images. Also, that you lose your hard work if your trial period expires.