Having played a fair bit on the moonboard over the last year, I'd say the problems are by and large very sandbagged. And also inconsistent across the grade range. There's an option on the website that allows one to "grade" the problem with what you yourself think, and this then shows next to the grade given by the "setter". In concept this should work great, but enough people actually have to give their personal grade. I think quite a few problems have been submitted by a few crazy strong folks, and a few who are known for sandbagging anyway.
Anyway, I have, always, been shit on 45 boards - I'm much better on anything less steep and with changes in angle (and bigger holds.
Here's a question related to specificity - how does climbing on a 45 transfer over to less steep stuff? Most of my aims are in the vertical to 20 over range. Does it matter than I'm weak as a kitten on the steep stuff?
Angle matters, but style probably matters more in this case. The moonboard is at the far end of dynamic/power climbing. no trickery or shenigans will help. I've got a friend who guides in Hueco and regularly boulders v11-v13 and couldn't do a single 7B on the moonboard.
So if your aims are poweful and dynamic, then there may be some use. If not, then your time would probably be better spent elsewhere.