So why is it so hard? Many reasons I suspect. Money is one factor. The market for "edutainment" compared to "blowing stuff up" is significantly smaller. A kid wants to blow things up (metaphorically speaking), and like it or not, the kid gets what he wants.
The number of parents buying games to make their kids smarter is just insignificant in comparison. And when the market is a lot smaller, justifying significant production investments of a high quality game just does not make sense.
At the reverse end, there seems to be an endless number of "companies" making (really low-budget) edutainment making a lot of unsubstantiated claims (lying) about both the quality of their games, the fun factor and learning value.
Thankfully, there are a few notable exceptions but they are usually pretty specialized (Scrabble does wonders for spelling, DragonBox Algebra, things like Kerbal Space Program, Quiz stuff like Kahoot etc).
With some luck, government/municipal teaching material spending over time will transition from mostly books to books+training tools, which should help investments into new and better products like you mention.