It is specific enough to not be just an idea but it might not be specific enough to avoid being obvious in light of previous knowledge (prior art). It also needs to be fleshed out in terms of the details of the best way you know to carry it out.
It might be that someone already had the exact invention and either published it or applied for a patent. Then your invention would not be novel. Alternatively, there might be an existing publication/patent/patent application that matches people based on them choosing a favorite flower or fruit. An examiner might argue that since some emoji's represented flowers or fruits your idea is obvious and therefore not patentable.
There have been many patents issued in this area in the past, see this one from eHarmony for example. However, it is getting harder and harder to avoid any computer related claim being labeled as "abstract" and therefore not patentable. An experienced practitioner in that field can be a big help, but no guarantee.