If the team stagnates on product development and continuous improvement, your team's overall confidence, dedication, and motivation will dissipate slowly. Taking this advice on, it becomes ever so clear on how to determine whether a team is going to be successful; also, it provides you that level of insight when to cut your losses short.
They say, "never give up when all hope seems lost". I'm a big believer in this; only if I'm the only person in the equation. For example, if I'm on the treadmill with no breath and needing to hit a specific benchmark (time or distance) -- I'll muster up an immense amount of motivation to hit that mark because I know in the long run it'll have a return on investment.
When you're in a professional, collaborative environment where you have to rely on founder (majority stakeholder) to pull their own weight as part of a business venture -- the situation gets increasingly more complex.
Ultimately, everyone has to make tough decisions and I'm passing this advice to anyone wanting to do any risky business venture, you should always be surrounded by people with the same level of passion and dedication. This will allow your team to gain momentum and sustain development velocity to really nurture a great product, grow your user base, and make a positive impact on your customers.