I think time restriction on learning curve is horrible

If you feel as if a SRS system (which is really all WaniKani is - along with a lot of custom mnemonics to help you learn) isn’t going to suit your learning journey then there are plenty of other options out there. Given what you say about time restrictions, you might consider using a textbook method like Remember The Kanji.

Check out The Ultimate Additional Japanese Resources List! as the work has already been put in as far as recommending printed material or even other websites with systems that you might find fit your needs better.

The kanji taught on WaniKani aren’t unique, nor locked (you can look at any item, with all the information, by going on the dashboard and searching or view items by level) and if you don’t need to make use of a SRS system, you’re still able to use that information.