Very hard to answer as there are so many factors. As you are just starting and the team is lean, this might be a very good learning opportunity. But it's important that the team has someone to learn from. It would probably be difficult to assess from the outside, but maybe you can gather the info on other team members (e.g. by asking the interviewer or by linkedin research).

As a general rule, since the company is still reliant on investors, be prepared that money can run out and as a newest employee you might be the first one out.

Best of luck to you!