It sounds nice but it comes with many pitfalls, especially with our society in its current form.
If schools weren't centers for removing critical thinking and individuality, then perhaps people would be able to find a purpose without needing to enter the economy. As of now, I can't see that being the case.
Just my two cents, I definitely understand why the argument exists.
You are right, the problem right now besides funding would be the way our education system works that doesn't reward intrinsic motivation. It would have to go through big change to allow a UBI to be good for our society.