When you want to describe a situation that is not favorable or advantageous, you might use the phrase "not propitious." However, there are a variety of other phrases and words you can use to convey the same idea. Some synonyms that might work include "unfortunate," "disadvantageous," "inopportune," "unfavorable," "adverse," "harmful," "unlucky," "poor," and "unsuitable." Depending on the context and tone of your writing or speaking, different synonyms might be more appropriate. It's always a good idea to consider the nuances of each word to ensure that you're conveying the precise meaning you intend.