Writing a manuscript is hard. There’s no more “academic” way to say it. Sure, it is easy for some who can just pump out a MS in a couple days, and sometimes it’s a really good (I’ve seen it happen; it’s quite impressive). But for the rest of us, writing takes time.
We all (should) put our best into everything we write, be it MS, grant, etc. However, this doesn’t mean that some writing isn’t better than others. Many things can affect how good or bad a manuscript will be, such as study design, stats (unfortunately), and writing itself. Once a study is complete, the design no longer matters (hind sight is 20/20). That leaves stats and the actual writing. Stats are a discussion for another day. So we’re left with the actual writing.
While some manuscripts are easier to write than others, sometimes you just know when you’ve written something great. I imagine that we’ve all had a manuscript or two that was a pain to write, or wasn’t received as well as we would’ve thought. But on the flip-side, we also know when we have something of true quality.
We should never submit something that we are not proud of. But that doesn’t mean that everything will be Science-grade (that’s why we have a variety of journals with a range of impact factors). Some will definitely be better than others, which makes the good ones that much sweeter.