Practicing going EN → JP is very useful if you want to be able to have conversations in Japanese and/or write in Japanese, and though WK doesn’t practice that, luckily there are sites where you can!
I recommend checking out KaniWani, which is the EN → JP version of WaniKani and requires you to input your public API key (which can be found here) to sync your WK info to get started
There’s also a newer alternative that you can check out, KameSame
I wouldn’t feel too bad about it. It would be hard to be better at going EN->JP than it is to read JP. How are you going to produce language that you can’t even read?
You will pick it up quite quickly. I don’t practice English to Japanese unless I’ve burned the item though. Sometimes it’s annoying cause a lot of words in Japanese roughly translate to the same thing in English so it can get frustrating when you have to keep trying every translation that you know for “to know” until it gets accepted. 知る、存じる、心得る etc.
I’ve never specifially studied translation into Japanese. I just make sure to have regular conversation practice and am ok with the words I actually use being fewer than the ones I can understand.
Absolutely it’s harder going E > J, but yes, it’s worth it if you want an active vocabulary rather than just a passive vocabulary (in Japanese). Mind you, if, like some, your only goal is to learn to read/listen to Japanese, never speak or write, then I’d say it’s optional. But even if you don’t speak or write, learning to translate E > J will reinforce your learning.
IMO It’s better to pick this up passively than to actively focus on EN → JP. I don’t think it’s particularly useful, especially pertaining to Japanese. Well, in general I feel it produces more bad habits than positive results.
Just to add from what @MissMisc had said, I want to share my experience. I remember kanji not only by English, I also remember it by my native language (Indonesian), I also remember it by no language at all not the language I know, but by its visual thing, could also by its feels on my skin and sound, like “wind” and “typhoon” for example. In short, I remember kanji by all of my senses.
That’s why KameSame helps me a lot to answer WaniKani reviews correctly.