The “real” one is AnkiDroid Flashcards. If you want to do any kind of customizing, building your own decks, etc. I still find it much more convenient to do that on the desktop and then just sync to a mobile device and do reviews there but that is optional.
There are some WaniKani based Anki decks, they usually will have tags per level. You can then suspend all cards in that deck and unsuspend them when you reach a certain level using the tags.
For Anki, there are also a couple of other really nice aspects such as the pre-made core 2k/6k/10k decks, having decks available to review the content of most of the common textbooks, subs2srs decks (my favorite cards are all from my Shirokuma Cafe deck; I just never get bored of them… ).
In general, I really appreciate the ability to be very flexible with how I set up my cards, having a lot of premade content available and having apps on all operating systems that sync with each other and work offline. Also having integrations with a lot of other applications such as https://voracious.app or creating Anki cards via Yomichan is super helpful.
I know that Anki is not as pretty as other apps and needs some getting used to – I was also hesitant in the beginning. But it is really worth it, imo. An nice way to ease into it is just importing pre-made decks and then if you feel like it, slowly start looking more into the available features.
In case anyone is wondering about buying the iOS app: for me, this was the best price/value purchase I made during my entire 2 years of studying so far. No regrets whatsoever about this one.