It's a lack of interest in, or emotion for, something that others find exciting
... like i lack inspiration, but i also feel like it's because i lack motivation... [DOC] [TLE] not feeling excited or enthusiastic - synonyms and related words ... [PAR] Comprehensive list of synonyms for not feeling excited or enthusiastic, by 
Macmillan ... lacking interest in something, or lacking sympathy with someone... [DOC] [TLE] Is It Depression If I Don't Feel Sad?