Composites don’t suffer from fatigue failures and are stronger than their metal counterparts.
The failures of the 787 are related to metal on composite joints, not the composites.
Some dumb people only hear the word “plastic” and fail to understand that Carbon Fiber is 100% pure carbon.
Everey materials suffers from fatigue. You’re absolutely right that carbon fibre is much stronger then the usual aluminium. But we have many decades of experience on long-term aluminium usage, something we don’t have with carbon fibre.