It's not the past anymore, we don't need to debate, we can watch and listen to actual recordings of therapy sessions and the patients going from feeling variously bad to better. Here's Dr David Burns channel with a 4hr video of a session with a woman who is obsessively anxious about her college-age daughter's safety: https://www.youtube.com/watch?v=on2N5DsKHRk

Here's a 2.5 hour session (split into several videos) with a doctor who has a bad relationship with his son and felt like a failure for it:

https://www.youtube.com/watch?v=42JDnrD106w

https://www.youtube.com/watch?v=S5H2YGljhqQ

https://www.youtube.com/watch?v=bZ9_0j_fmeg

https://www.youtube.com/watch?v=eiCrdGVa8Q0

https://www.youtube.com/watch?v=cARvhlTckaM

Here's a couple of hour session with Marilyn who was diagnosed with lung cancer and spiraling with depression, anxiety, shame, loneliness, hopelessness, demoralization, and anger, despite her successful career:

https://www.youtube.com/watch?v=S7sQ_zDGsY8

https://www.youtube.com/watch?v=tyuFN4mbGZQ (there's probably more parts to find through YouTube somehow)

And a session with Lee with loneliness and marriage relationship problems:

https://www.youtube.com/watch?v=imEMM3r6XL8 (probably more parts as well)

It's like saying "it is still debated if debugging even works" as if all languages, all debuggers, all programmers, all systems, are the same and if you can find lots of people who can't debug then "debugging doesn't work". But no, you only need a few examples of "therapy working" to believe that it works, and see the whole session to see that it isn't just luck or just the relief of talking, but is a skill and a technique and a debugging of the mind.