My own feelings are that many in their early stages could do better just with their renderings: pay attention to dynamics, to an appropriate duration of notes, not to try to bluff themselves at the mixer to try to make good deficiencies in their attempts at scoring.
Some cheaper notation software makes a pathetic attempt at balance. To me, so much comes down to balance. So the original score with its official dynamics needs copying for presentation with the dynamics exaggerated to get a decent audio balance.
I'm disinclined to respond to a wannabe who says "I threw this together this afternoon. What d'you think?" Maybe I'm being unfair because such a person might come up with a beautiful melody or something else interesting. I'd be ready to comment if they said what they were aiming for and to have their own honest feelings about it. I'd also be happier if they'd allowed a little time for reflection - so often even a week gives a composer time to stand back and view it through fresh ears.
However, we also need awareness that we aren't the composer and/or hearing the same as the composer. All is subjective (with certain exceptions) and our comments are based on our views. Plus, the media through which we listen won't be the same as the composer's. We try to make allowances. My tendency is not to review a genre in which I'm not versed although listening is always a good idea to expand a reviewer's auditory horizons.
And it doesn't need reviewers to say that all artists should aim to be self-critical. Being honest (about one's own work) isn't always easy but trying is necessary so when they present work for review it's as close to what they think they want - won't be perfect, there are always limitations - but at least as good as their current experience allows.