Regarding bottleneck, some areas are massively funding constrained e.g. I'm not sure I could name a single mental EA mental health charity that is talent constrained. People who graduate with firsts from the world's top 3 or so neuroscience/psychology departments, with a ton of work experience, are passionate enough to be willing to volunteer 20Hs per week but one can't hire and train them up as there simply isn't enough funding.
This advice is targeted at:
Why should a disinterested third party, without firsthand experience, recommend these therapies over CBT given the relative lack of evidence?
E.g. Other than those who practice them and their clients, do they have any reputable backers? Has it been shown by disinterested parties to work better on certain types of people? Is there any other source of evidence that backs the notion that they are predictably superior for at least a subset of the population?