The late, great Barry Finn would sing with anyone- I've watched him!....but as you see, he would 'enjoy' singing more with those who mostly knew their songs..

Record yourself singing...then ask yourself if YOU would enjoy listening to someone singing in the same manner, If not, work on it! Ask people to critique you away from a song circle. Think about the song and what it means and try to put the 'feel' of it into your singing--humor or pathos need different treatment. (Just reciting the words to a vague tune is not fun to listen to.)

I am reminded of a thing I read once about writing... the guy said to ask yourself, "Do I really have something inside me that needs saying, or do I just 'want to have written a book'?" Ask yourself if you really enjoy singing, or you just 'want to have done a song in a group'. It's not always an easy question to answer, but it may help form your approach.