Not lowering the bar, just providing a step stool.

There have been a couple of times when we have reviewed papers that are essentially publishable as initially submitted; the "criticisms" were more along the lines of constructive suggestions that the authors might want to consider when they submitted a revised version of the paper, but those changes were not required. However, a much more common experience is for the authors to receive a series of comments from multiple reviewers. Most of those comments are critical for the authors to address, to ensure that the data in the paper are of sufficient quality and rigor, with adequate controls, to support the stated conclusions. That said, reviewers sometimes make requests, with the best of intentions, which might be reasonably considered as "beyond the scope of the present study". Thus, there needs to be a balance between addressing each and every comment of a review and completing a story even though there are additional avenues and questions that remain unexplored. Sometimes, even after a repeated round(s) of review, such questions linger and may impede acceptance of a worthy study.