Is Descartes just proving what we already know, or have we discovered something important on this journey from doubt to absolute certainty?

from page 23 meditation number 5 begins until the last one which ends in meditation 6

So Descartes spends the whole time in this book, which you’ve now finished reading, trying to prove two simple things and one not-so-simple (rather huge) thing.

The simple things; and a whole wide world apart from exists, including other people and other things. The not-so-simple: God exists.

But at the end of the day, do you think that Descartes achieves his goals? What do you think of how he tries to achieve his goals — first, doubt everything; then, come to be convinced that at least then prove that God exists and doesn’t deceive me or anyone else (the ultimate non-fake news source); and then, since finally and at long last, that there really is a whole wide world out there, waiting for me to explore to and to know it more deeply.

Is Descartes just proving what we already know, or have we discovered something important on this journey from doubt to absolute certainty?