That's the point of the post. There's lots of money out there. But it gets spent in ways that are different from what the typical entrepreneur and VC expect it to be spent on. The dynamics of how purchasing decisions are made are around cost, not quality.
Let's talk data. How many students spend money on educational services? 15% of students take SAT or ACT prep outside of school. By the time a student is 16 and has some discretionary spend and has some influence of a parent's spend. If students took their spending power/influence and prioritized educational spend you would have a lot more than 15% of students getting test prep outside of the school.
Consumer spending is huge. Consumer spending on education is large. Consumer spending on education where the primary driver is quality is much smaller.