Why peacetime promotion slowed the Georgian Royal Navy

What caused Royal Navy stagnation between the Seven Years' War and the American War of Independence?

A generational turnover combined with seniority rules that kept talented junior officers from replacing weaker seniors during peace.

The stagnation reflected Lord Hawke's tenure in part, but a difficult generational transition mattered more. Many experienced officers retired after the earlier war, while some of the available senior officers were not the strongest candidates for command. Promising junior officers could not simply leapfrog the list because promotion normally followed seniority unless exceptional wartime service justified advancement. Peace removed many opportunities to earn that distinction, leaving the service with a promotion system poorly matched to rapid renewal.