Anki seems to get a bad rap, often for being ugly/clunky and having a steep learning curve depending on how far you want to go with it (you don’t have to learn every single thing to get good use out of it though). But it’s a pretty amazing tool - it might take a little getting used to, but it’s super flexible, there are a lot of amazing plugins available (the Japanese support one is a must), and any deck can be made as beautiful as most competitors (the templates use basic web languages HTML/CSS/JavaScript and I have spent way too much time just making stuff beautiful, can’t help myself).
If you do ever decide to use Anki for premade decks, like @Kumirei already said, they’re usually ordered already.
If you want to progressively unlock cards with a certain tag, you can suspend all or some in the note browser to “pause” them. Most vocab decks based on books will have tags for chapters etc that you can use to filter with (you can temporarily cram a whole chapter for example, with a filtered deck).
Kitsune is probably great too 
But Anki isn’t as bad as the internet makes it sound, and it’s also free and open source (any developer can contribute improvements to the software, and we can all spend our money on more books 
).
From the posts I’ve seen around here, the creator of that Kitsune deck used to be a heavy user of Anki. He made some wanikani-styled decks (with text input): https://community.wanikani.com/t/some-supplemental-material/8121
He also made some (still) helpful tutorials: [Anki] Tutorials. Here’s one he made for suspending cards: Anki: Using the Suspend Tool - YouTube
EDIT: sorry, I emoji too much (blame Slack)