Feckless carries a negative tone, suggesting incompetence or irresponsibility. The project failed because of his feckless management.
Pro Tip 2/3
Not for Skills
Use 'feckless' to criticize character or actions, not lack of concrete skills like playing an instrument. Their feckless spending left them in debt, not their lack of budgeting skills.
Pro Tip 3/3
Casual Use
Best used in informal situations or literature, might be too strong for polite conversation. In casual chat, calling someone feckless might come off as rude.