I've been digging in to the literature on the impact of psychotherapy training on outcomes.
A lot of the meta-analyses I've come across would really qualify as Garbage In Garbage Out status (where was PRISMA when all these SRMAs were being published in the 90s!?).
For example, there is an interesting review from 1995 on the topic. They state, "It is concluded that a variety of outcome sources are associated with modest effect sizes favoring more trained therapists."
(PDF) Graduate Training in Psychotherapy: Are Therapy Outcomes Enhanced?
When you really drill down into the individual studies and set a high bar for inclusion, there is evidence for a positive effect of training on outcomes. More training = less drop out. More training = more improvement in symptoms rated by independent clinicians.
Of course, some of the over all effects were not significant, but the heterogeneity of the populations, settings, and how "training" was rated was massive (e.g., in one study, training was a continuous variable of "years since began practicing" and psychiatrists, social workers, and psychologists were all thrown together in the same bin).
Also, the sample sizes for most of these studies were not very large (n<60 in many cases), so even with multiple effects trending toward favoring training the headline was "not significant".
The more I look in to this topic the more I think this shouldn't be ground that should just be ceded. Yes, of course there are many amazingly skilled LCSW folks. However, there's also evidence that more training = better outcomes. Just because it's hard to do research on this topic it doesn't mean we should give up as a field.