Canon has nothing to do with good or bad. It's not a value judgment.
The makers of "Threshold" might disagree with you.
And it's funny, because the books matter almost exactly as much to Trek as they do to Star Wars; George Lucas feels obviously free to contradict whatever the hell he wants to in the books when he's making movies or animated things, exactly as in Star Trek. And the Trek books, with only a very few notable exceptions, treat each other as part of the same continuity, exactly as Star Wars does.
Exactly...it's all about the perception of the intended audience as to the "significance" of the books, as opposed to what the actual producers end up doing, so it's a little weird to me that CBS doesn't just go ahead and say
that they're canon, since that level of canonicity is treated the same way in practice as franchises like Doctor Who
and Star Wars
The cancellation of the Abramsverse novels was apparently motivated by concerns with consistency, so it's starting to seem as if the current Supreme Court wants to adopt a Lucasfilm-like approach to their own tie-ins.