Even with those experiences I would never say there's a correlation between chosen language and success, because in all those cases it was the core business idea that was the driver of success or failure.
I do still try to choose the right tool for the job based on some kind of instinct and experience anyway.
Also, congrats on your gig. From where I'm standing (an old fart still grinding it out at startup #7) that sounds totally awesome. This is going to be my last startup though, I was going to accept my fate and go work for some BigCo before it's too late otherwise I'll have no retirement at all. But if I could find a nice niche like that, I'd happily work part time forever.
I will also add that I am mostly a PHP dev and I do not work with WordPress at all. There is a LOT of work out there, though.
I make a very comfortable living, wife stays home, we have no debt and I work around 20 hours a week most weeks. Most of my clients are on retainer and I do good work for them. We rarely talk about what "stack" we're using but we always talk about the problems they're trying to solve.
Most of these arguments are about ego, someone being right and wrong and what tools are the best. From an old fart I can tell you this... tools are only as good as the person using them. If you are a shit developer, nothing is going to save you from yourself.
It really seems to me like a huge issue these days is that people can't even stick with a framework or language long enough to ever be decently good at it. This seems to be due in part to your #1 - learning what is needed to get a job and #2 - fear of building a product on the "wrong" stack when they scale to billions of users in 2 weeks (hint: this doesn't happen).
The biggest lesson I've learned from building a product is that no matter what tool you are using, you cannot engineer your way out of a marketing problem. No marketing = no success. There is a lot of horribly coded garbage out there making people tons of money because of marketing.