The problem with looking at words is that you are learning language to language translation instead of language to thought. When I think of "pencil", I have a schema of a pencil appear in my mind. When I see enpitsu (well, the hiragana or kanji for it), if I have to think "pencil" to bring up the schema of a pencil that is an extra layer of thought that slows one down. With more abstract concepts there might now be a better solution, though with more abstract concepts you also have greater issues with things not being one to one translations.

>Just use flash cards.

That is effectively what the apps are mimicking and what I am using. What I'm bringing up in a desired feature I haven't found (granted, I've only checked out a dozen or so apps which is worlds apart from serious market research). As for why I use an app over flash cards? Phone is more convenient and always on me. Also, other than a stack of the most common kanji, flash cards don't really scale in a portable format.

But I probably should buy a deck including kanji for at home usage.

Sure, the ideal end state is that you know the Japanese word intuitively without English or another language as an intermediate step. But starting from a totally unfamiliar word, dictionary definitions and example sentences are both fast to access and easy to copy down. (For a sufficiently advanced learner, I would encourage using Japanese language dictionaries instead of Japanese-English ones.)

And I'm only recommending flash cards and other rote tools for kana, because recalling them instantly is both important and relatively low-effort. I don't have a strong opinion on how to learn vocabulary, other than to prioritize based on actual usage: media you read/listen to, conversations, etc.