I disagree with this. Anki's power comes from spaced repetition. Spending your time creating cards instead of actually reviewing the material is very inefficient. If high quality decks exist for the topic you're learning, use them instead. I've learned this the hard way.

Fields like medicine and language learning (you will still need to create your own deck for sentence mining but that's different as it's not a time sink) have great decks. For actual "niche" topics though, creating your own decks is your only choice.

For people who are going to create their own decks: check the Anking deck to see how to create "great" cards.