"there was nothing good I could say about it so I would rather not review it at all."
Like it or not, that is the policy of most music magazines. In some cases the reviewer can't write a good (in the sense of useful and well-informed) review because they aren't familiar with the type of music and declining is the best policy.

"the people concerned had obviously put a lot of work in and tried their best."
Could be worse, then. For a magazine which I edit, we were sent a CD featuring a singer with guitar which was badly out of tune on most tracks. He claimed the album was "professionally recorded", but if I was being paid to record someone I'd have called a halt after the first line and tactfully but firmly persuaded them to tune up properly before going any further. There is no excuse for that!

"I discussed the album - privately - with someone who told me they enjoyed it."
That's another reason why not to write a bad review. Instead, pass it to someone who appreciates it and let them write about it.