When learning new vocab (I’m currently in a real vocab hole and apparently have to learn 450 (!!!) new words before Wanikani will give me any new kanji) I rarely even look at the context sentences as they nearly always include kanji that I don’t know.
Ideally they would only show me things I know how to read, but failing that furigana readings would be very useful. I guess this is a big ask, but it would certainly be useful.
As they stands they’re pointless, and rather demoralising.
I think adding furigana would be helpful. The context sentences are selectable though, so you can copy-paste words you don’t know into jisho.org or some other online dictionary if you’re stumped. That might help make them a bit more useful. I think any reading experience you get is helpful, even if you have to look up some words. Not saying you have to read all of them (or should) but yeah, I hope that helps.
I use Rikaikun and jisho for example sentences, but when there are multiple readings, or long sentences it takes a while. I think adding furigana would be a great feature and I would really like to see it implemented.