I think it's very true that therapy fails a lot of people, that there are problems for which therapy is ill-suited (can't really articulate what these are but generally those things that people can't control and for which changing one's relationship to the thing or one's reactions to the thing can't be done). When I was in grad school in a related field, the clinical psychology students spent a lot of time talking about this issue, as the institution where we studied was big on institutional failures of all kinds, especially mental health.

But I think that if therapy failed you, you are not, as you say, a failure at life or a failure as a person. You did what you could and certainly gave it a lot of your time and undoubtedly your attention and money. It reminds me of when my husband was diagnoses with Stage 4 cancer (and he lived only 4 months afterwards), how some people and to some extent the larger culture propagate this "if you have a positive attitude you can beat cancer" or "if you live a psychologically healthy life or have a nutritional diet you won't get cancer." I found this attitude, and the dipsh*ts who sent me articles about how lemongrass cures cancer or offered me a wholegrain cookbook I already had, very hurtful. There was more of this than I'd care to remember.

I think it is deeply ingrained in our culture that we "blame the victim." If something bad happens to you or you can't fix it afterwards, that's your fault. We want to believe in a "just world" where only the undeserving or those who lack effort have bad outcomes in all kinds of things. It feels terrible to get caught up in these social attitudes.

I hope you can let yourself off the hook for "failing" as a person. Sounds to me like you did the best you could and the institution failed you.