The efficiency depends on the issue, model and personnel. Studies suggests that it helps for repressed mental issues, traumas, depression, anxiety and more. However it's not premised to turn you into Chad, tho it can make you less creepy according to behaviourism.
The most effective treatments are more expensive than simply talking that doesn't do much beyond venting.
The goal for therapy should be to obtain catharsis for painful emotions, as such one can seek models that addresses the body and brain.
Also incels should read and learn some basic psychology to get more insight on how the mind functions and becomes overburdened with negative impulses and impressions over time, it's a downward spiral that sours everyday-life and mood.