Watching others go rich, while I stay broke and left behind.

If no one else cares about collecting from existing clients then it needs to be you since you're the one that depends most on it. Call, email, go into their office every week...whatever you have to do get paid so that some of the financial stress you have is alleviated.

This will help you start to focus. You need to start getting small "wins" to dig yourself out of this hole. Focus on things that are simpler to achieve, such as doing a project for one of your reliable clients and kicking ass for them. Then, once you get yourself to a better place where you're more confident, confront your partners about the new direction of the business and how it's not sustainable.

If they don't budge and you have to go get a job somewhere else to get your bearing straight then so be it. That's not a terrible outcome.

I was working 18+ hours a day every day for 2 years with a stressful client. I've had the hair loos and also heart palputations when trying to sleep at night. This is not a good place to be. I would say no.1 make sure you look after your health and make sure you sleep properly. As the saying goes, people lose their health trying to become wealthy, and when they become wealthy they would spend all their money trying to get their health back. You come first. Your business is second.

Could you get another job in the meantime? e.g. as a freelancer/consultant?

Did you have a vision statement in the beginning ? Did you follow it ?

I think companies have too many meetings shootin the bull instead

of doing actual experiments where the product should go. And yes, the

new trend "make it sexy-pretty and useless. Good luck !

"I am the only one who isn’t independently wealthy"

I would say that partnering with people who aren't as hungry as you are can be a problem. Inevitably it's the person who needs the venture to work out the most is doing the most work. I've made that mistake before as well. Try to negotiate for a higher equity interest if you are putting in more time/money. If your partners won't negotiate (greedy) or refuse to see the truth (assuming it is the truth), then just cut back on what you are investing and put that energy somewhere else that only helps you. Good luck.