Metacognitive Therapy. Effectively, when dealing with persistent unwanted thoughts, it teaches you to let them pass without judgement / evoking response, and to divert your attention elsewhere. I find that this complements CBT well if one has already done the work of recognizing that some thoughts are unrealistic distortions. Proponents of MCT seem to bash CBT needlessly; they needn't be mutually exclusive, and at any rate, evidence suggests that CBT is generally effective (and there's a much larger body of it than for MCT).

> someone who keeps you accountable and committed to a course of treatment/training. Many people could probably do these things by themselves, but many others struggle to keep it up for one reason or other.

It depends on preference and self-efficacy, notwithstanding that intrinsic motivation is necessary whichever way. However, most people don't seem to realize that self-administration is an option, and walk away from the prospect of therapy entirely if they deem it too costly.

The other problem is, as with personal trainers, whether you'll have a good one is a roll of the dice. Trainers have a perverse incentive to divert people to use machines and away from compound movement exercises like deadlifts. Similarly, many therapists don't offer much insight or homework. And all the while you can leverage the most powerful approaches by yourself at zero cost.

Seeing a pro is still a decent heuristic, most people will want to avoid the labor of doing research which can be daunting, tiresome, and is a skill in itself. Pressing the "just tell me what to do, here's money" button is arguably more optimal depending on the circumstances.