Even partial credit seems enough to question the wisdom of Marcus Aurelius's philosophy.
He raised Commodus, and co-ruled with him for a time.
- He was was either unaware of his son's (lack) of fitness or
- He was aware but unwilling to take corrective action or
- He was aware but unable to take corrective action
Considering the extreme excesses of Commodus came after his father was no longer in the picture, Marcus Auerelius being unaware of what his son would do in the future seems rather likely.
He raised Commodus, and co-ruled with him for a time. - He was was either unaware of his son's (lack) of fitness or - He was aware but unwilling to take corrective action or - He was aware but unable to take corrective action