Is it reasonable to submit a paper to a journal that I have uploaded to the Arxiv 4 years ago?

I have a paper submitted to the Arxiv 4 years ago (with another co-author). At that time, the only reason that we put the article online was that someone asked us to do that in order to cite it. Since then it has been cited some times, including authors that claim that have found (independently) the same proof as ours. The paper is the solution of a combinatorics problem. I have been thinking lately that it would help my career to get this paper published in a Journal, but Im not quite sure if this is a good idea, since it is certainly not a new result (and it is not super-intereseting, just a nice solution for a problem). What should I do? Has anyone been in the same situation?

Any advise is very welcome! Thanks in advance

PS: In case that is a good idea to get it published it would be nice to have some kind of advise of which journal might consider articles of the types I described, as I guess that lots of Journals won't even consider it.