If you receive equity, then sure, take this into consideration.
But OP isn't a professional investor. He isn't risking other people's money. He is betting his own financial stakes on the venture.
The outer scope is as you say -- will this company go on to greater heights?
But the inner scope is -- given my personal appetite for risk, can they make pay day?
This person is, I presume, young and without obligations like children or a mortgage. So his or her appetite for risk has much more latitude. But that doesn't mean it isn't there.
I opined on this a while back and was downvoted heavily for suggesting that interviewees ask to see some sort of financials -- the consensus in the ensuing discussion was that it was ok to ask what kind of runway the employer had as a proxy for the underlying financial realities.