Well, sure, politicians are typically lying or promising things they cannot deliver, and they generally do just enough to stay in power and get rich. But there's a difference here.
Thaksin is held up as a man of the people, a folk hero, someone who cares about the little guy and shares the wealth around. Someone who would never behave in the terrible and unscrupulous way that the current government would.
So the truth is quite important here. "Thaksin behaved the same way that all politicians do" is not the get out of jail free card that it might sound like, given his carefully constructed reputation.
Anyone who wants to play the "man of the people" role in Thailand, but doesn't do something about the education system, is being dishonest. Especially someone who has been to the best schools in Thailand and then educated abroad. The logical conclusion is that fixing the education system, while desperately needed, wouldn't have bought him votes, or at least it was not as cost effective as other measures, so he didn't bother.