Only makes sense if it becomes big, right? Surely it is highly impractical for people to court hundreds of miles apart.
Also, how would they interact on the forum? Make a post about themselves? If it becomes big, how would people filter by age, location, beliefs, etc. on a forum?
There are plenty of catholic dating sites for those interested I'm sure, the real problem is likely the quality of the people desperate enough to make a dating profile, not the site. A new site won't fix the problem.