First of all, preregistration is not a requirement for the scientific method, which has functioned well for centuries. That is a recent trend in response to the overflowing amount of haphazardly published science.
Second, it is up to the individual scientist to decide to preregister or not. Some social scientists may preregister.
Third, small sample size may be a fair critique, however that overlooks how difficult it is to collect such data.
You've made a lot of generalizations here that amount to, "social scientists aren't as rigorous as other areas of science, therefore we should only believe studies that disagree with their results". I don't think throwing the baby out with the bath water is helpful. You can take results of studies with small sample sizes with a grain of salt, watch for replication, etc. Lambasting the field as a whole doesn't make sense to me.
Finally, readers should note that this isn't a new argument. People have been making this claim about social science for 120 years, if not longer, but at least since Freud and contemporaries began publishing.