Past Therapy hit a dead end because my wife wouldn't participate, why try Therapy again?

This is a tricky question.  Therapy can help you understand yourself, address any trauma in your life, challenge beliefs and thinking patterns, and learn how to better cope in your own life.  But, as you have alluded, there are limits to progress being made in a relationship if both parties are not participating.  Sometimes spouses are reluctant to start therapy with a therapist that has worked with someone individually because they perceive (whether real or imagined) that the therapist will be aligned with their spouse and not able to remain neutral.  There is some validity to this thought, as the therapist you had worked with had looked at her through your eyes and not been able to hear and discuss both sides of the issues.  It is not a clean slate and would probably not be the best place to start couples therapy. 

If she is not interested in starting couples therapy, I would assume a few things might be true.  Maybe she does not like therapy and does not see the value,  maybe she is angry and wants to stay angry, maybe she is happy in the marriage and feels her needs are met, maybe she has decided that nothing can fix the problems and nothing will change, maybe she is avoidant and does not want to look deeper into the relationship problems, maybe she believes that people just are what they are, etc.  If any of these are the case, it is unfortunate.   My hope is she would be willing to start couples therapy from a fresh place with a new therapist.  That is probably the healthiest place to start couples therapy.  It allows the therapist to have a completely new set of eyes on the situation without any bias and hopefully remain neutral through the process.  While I am sure you were 100% honest with your previous therapist, you can really only be honest about your perspective of the situation.  In my opinion, this might create an imbalanced playing field to start the work.  I hope your spouse would be open to a new playing field and really allow you both to work on the issues. 

So, to answer the question asked, it all comes down to what you are wanting to gain from therapy.  If you plan to really make significant progress in your marriage with only you working on the marriage, I think therapy would have significant limits.  Marriages get better as both parties are committed to a process of change.  While you can gain insight into some of your patterns and learn relational skills and see some progress, it is truly hard to work on a relationship if one of the spouses is uninvolved in the process.  If the marriage has problems (and I surely don't understand those problems), generally both spouses have to be willing to work on them.  If one is not, maybe you should be asking the reasons why and what are the barriers to getting better.  It is hard to make anything work very well if both are not committed to change.  Now, from a personal perspective, additional therapy could be very beneficial.  It might allow you to work on things that were not worked on before.  It might allow you to go deeper than before and deal with more core issues.  If you have trauma based issues, it might allow you to heal more.  I hope the past therapy did show you more of how you attach in relationships and why you do some of the things that you do.  I also hope it helped you see your patterns in relationshionships and gave you strategies on how to be a better partner. 

I hope this answer gives you some insight on what your next move is.  I wish you and your wife the best going forward.