Is it a terrible idea to aim for a lower journal for a paper? Okay, I'll try to explain what I mean quickly. My research on a topic kind of strayed from its original purpose, and for some reason (bad choice, lack of experience, lack of guidance, etc) I stayed with it way too long. That was my mistake. It's done now. The question is where to go from here.

I don't think what I produced is worthless, but it's certainly not something the scientific world is sitting on the edge of their chairs for. I think it should be put out there but I'm under no delusions that it should be in Science or something.

I submitted it to one mid-level journal and it got rejected, but it was also because it was in kind of bad shape from a writing (i.e., not science) standpoint.

So I have two options: I could submit it to another mid-level journal, but that would require a decent bit of work. They tend to be a little pickier and of course there's a much higher chance it would get rejected again, meaning more work to submit to yet another.

Or, I could submit it to a lower tier journal that has a much higher chance of getting accepted. As the tone of my question probably implies, I want to do this one. I made a mistake staying with the research this long and I want to be pursuing this new direction, and submitting to a mid-tier journal will mean sticking with it even longer. Aside from the fact that I want to pursue this new direction, I absolutely hate pouring more time into this old thing.

So my question is, how bad is it to have a paper in a lower tier journal? (I don't mean an open-access, pay to be published one, but the next level above that.) Is it possibly so bad that it'd be worth it to put in the extra work and aim for the mid-level journals, even if it'd take a few tries?
From my point of view, there is nothing wrong per se with submitting to a low-tier, non-spam journal. I have always maintained the position that if you find out mid-way that your work isn't what you want / should be doing, it's better to submit what you have to whatever is achievable at this point than to either stick it out or throw the work away entirely.

However, in your case it actually sounds like you may want to go for another iteration at the mid-tier anyway, because you don't think your work is that bad, it's just the write-up - and this can be fixed with a modicum of effort, in the worst case re-writing the paper. Also, assuming you are an early-stage researcher, getting more writing practice is basically never wasted effort. In the end, we are not talking about investing a year more into this project - it's a few more weeks for re-writing, and then some on-and-off effort for revisions. Finally, would it not be annoying to you to "waste" your work to a low-class venue just because you did not want to write it down properly?