George Bernard Shaw said (a lot of things but also) : "the golden rule is that there are no golden rules"
it is all about context & of course there are plenty of permutations and combinations that stink. The problem I find when I am asked for comments is having that empathy with the writer to help. Lyrics without music are just words. Target audience, kind of accompaniment etc can frame the answers so much.
Persist with the songwriting workshops - some are more constructive - some more practical most seem to be discussion groups but be prepared open ones mind and consider possibilities.
consider colaborations, if you can handle the strange ideas coming at you and if you don't try to posess your own "bits of" it can be instructive. If you get into fighing over words/lines it can be a dampener. record the words and move on, suggest alternatives and record them and move on.
At the end of the day - if (and it is not a must), if you intend singing to an audience they will tell you things, just ignore those negative people, initially.
I always remember singing an anti-suicide song and two girls of the same age as the subject told me it was "right" - not good, nor well sung but "right" and that's all the feedback I needed.