Renshuu.org is probably the cheapest and all-covering option, but not sure if you would like it.
Anki is as good if you know how to use it well. Not sure how much Kitsun.io makes better even with a good UI (and no direct Yomitan / AnkiConnect alternative). Regarding Kanji learning, I post this one a long while ago, but really, a way is to already know or cram vocabularies first, to be later reinforced by learning Kanji. WaniKani decks use copyright materials from WaniKani API, which I would feel guilty to use without an active subscription.
I can relate to addiction tendency, but perhaps it’s also that concentration that focuses to work hard.