but there's no way for a reader to know if you're an inept experimenter, got a bad batch of reagents or specimens, had a fundamentally flawed hypothesis, inadequate statistical design, or neglected to control for some secondary phenomenon.

I agree, to the extent that single, poor dataset can't draw useful conclusions. But after (painstakingly) controlling for issues with this dataset and from lots of other similar datasets, there can still be some value extracted from a meta-analysis.

The prospect that someone might one day later incorporate your data into a meta-analysis and at least justify a follow-up, more controlled study, should be sufficient to tip the scale toward publishing more studies and their datasets. I'm not saying hot garbage should be sent to journals, but whatever can be prepared for publishing ought to be.