I believe the issue is not a lack of content, but the quality of the content. There are so many decks on https://ankiweb.net/shared/decks/, including ones for Kotlin (https://ankiweb.net/shared/decks/kotlin) and Trigonometry (https://ankiweb.net/shared/decks/trigonometry), but most of them are of low quality or not what I want. Sometimes it's easier to just create a deck by myself.