Yes, but you won't train them by dating a lot of people. Dating a lot of people trains you that people leave, it will teach you that strong relationship hurts more when it breaks.

Also, if you dated a lot of people who were genuinly unsuitable for long term relationship, issue really is either your selection or what you signal to good prospective partners. Like, abusers pick up certain types and stable guys/gals avoid certain types.

I believe that therapists are better at convincing patients that therapy helped than they are at generating improved outcomes. Furthermore most therapists are not using treatments that there is much evidence for.

This is not to discount that there are treatments that really do work. CBT (Cognitive Behavioral Therapy) is an excellent example.

This is also not to deny that people who seek therapy on average do better than people who do not. That is clearly true, but it is unclear whether it is explained by "therapy worked" or the selection bias that "people who are demonstrate putting effort into their problems are likely to do better."

But it is a lot easier to make the claim that therapy helps than it is to demonstrate it. And given the combination of the replication crisis and widespread poor use of statistics, it is hard to trust most of the research into mental health treatments.

That said, most people who have been through therapy believe that it helped them. This is not actually evidence of effectiveness. Because that was true even for therapies such a Freudian psychology that are demonstrably ineffective. And even widespread belief in the effectiveness of treatments is not evidence either - as https://psmag.com/social-justice/75-years-alcoholics-anonymo... points out there is remarkably little evidence for 12 step programs for addiction. Despite testimonials and general belief to the contrary.