The failure rate of the average start up is heavily against you.
My outlook is that you will have to work through a few failed start ups before you finally build/find employment with a successful one. That being said, it can be soul destroying to see a product/system you’ve worked hard on to never go to market / go live.
Oh, for sure. I have been there more than once with the technically sound product that isn't going anywhere. It's awful. So another way to put my question: Once you figure out why the current startup isn't going to make it, why stay? For some people the answer is, "They keep paying you." But for me the answer is, "You probably shouldn't. Move on to something with a chance."