If the purpose of Jesus was to spread knowledge and wisdom about something that people really should know, and still "there are few who do", then that sounds like a failure to me.
Of who? The teacher or the students? Do you blame everyone else but yourself for your shortcomings?
And I never said they "should know" it. That's your words you curiously supplied. What I mean is that it's something we all already are, but are too caught up in our own selves to see it. That fault is ours. When it finally happens, when the light bulb goes off, the first response is "it was there the whole time, and I just couldn't see it!". All that teachers of Wisdom can do, is to point you to it. But you have to open your eyes and ears to apprehend it. They cannot give it to you. You already have it. But my original point was these "teachers" did not begin in the year zero. And then like today, it's few who 'get it'. It's not the teacher's fault. But the student's preparedness to receive.
If the difference between the level of knowledge wasn't very big before vs after Jesus, then Jesus wasn't an effective way for God to achieve his goal.
Aside from the fact that his teachings created a massive social and cultural sweep that ended up becoming the State religion of Rome and spread through the entire West, lasting up until today that it affected the world you live in? Aside from that he wasn't very effective, you mean?
If the difference is big, it's grossly unfair to those not fortunate enough to live in the time or region where they had access to this.
I'll put it this way, I believe the message is the same throughout the ages, but how it is communicated is within relative cultural frameworks. There are many voices living 'locally' to your own time who are likewise able to speak of it in your language and time. But as in all ages, not all are ready to receive them, not to the fault of the teachers.
Didn't Jesus teach of the sower of the seeds, how that some fell on hard ground and died, some fell into the thorns and was choked out, and some fell on good soil and took root and grew? The sower of seeds casts them to the wind like in nature which is indiscriminate. Where it falls and either grows and dies out is the responsibility of the one whose soil and ground it is. If you never tend to your garden, it's not the seed manufacturer's fault the seeds don't grow. It's yours.