Synonyms of 'inefficacy'
Futility is a total lack of purpose or usefulness.
the injustice and futility of terrorism
spitting in the wind
If someone has feelings of inadequacy, they feel that they do not have the qualities and abilities necessary to do something or to cope with life in general.
his deep-seated sense of inadequacy
Thesaurus for inefficacy from the Collins English Thesaurus
lack of efficacy ; inability to produce the desired effect