I was at a startup that failed, I was actually the last non-founder to leave. Not because I didn't see the problems, but because I was the last one of us to find a new job. Everyone began looking for a new opportunity around 6-12 months before our runway actually ran out.

Here were some of the issues:

Over time, the information flow from our founders degraded in quality and quantity. When you're at a company of 5-10 people, everyone should know everything.

When engineers left they weren't replaced. Tech transfer was just a formality, and projects were shelved entirely. If a startup isn't growing, it's dying.

The founders attempted the same monetization strategy for about 2 years with zero success. Not as in "unsustainable" but literally, not a dime!

So TL;DR: if your company is shrinking, non-founders kept in the dark, and nothing seems to be changing in strategy when no one is paying you, the company is probably going to die and you should move on. However, staying around until the end of your runway will lead to a glowing reference for future job searches.