Well this is why it's important to work on something that you believe in. I think there is a fatalism to think all small companies are going to fail. Individual employees should use their own judgment when thinking about whether a startup will work— they are often more right than not since startups tend to be self-fulfilling prophecy. If lots of smart people like you want to join too, then it actually becomes a lot more likely.

That being said by the numbers most startups fail, and there is no guarantee a startup role will get you a positive outcome vs other alternatives.