What I learned is, my time is mine to protect and my skills are mine to dedicate where I see fit. Noone can oblige you to spend these things on what you don't want to.
People will always blame others for their lack of application. If they were true entrepreneurs, they will find a replacement for you.
But you are unique that you want to leave what is really a pet project (I've been in those too many times) and build a real business. You should!
Don't worry about what others will think, you can't control that.
A start-up is about bringing something its founders are passionate about to market. Anyone who thinks a start-up are a way to make money, are in start-ups for the wrong reasons. This sentence has failed start-up all over it.
The mindset that also comes with this idea generally leads to alot of burn out for those passionate and those who are feet up lets get rich with minimal effort. Which is was the fate of my start-up experience. 3 of 5 founders were passionate and hardworking, and 2 of 5 considered it a 'side thing' contributing much less (and even nothing when half-assed). When time came to find buyers to start cycles of improving the product e.g.'fitting the niche of our product', things fell apart. The same 3 of us called out that we are failing and don't see a path, and the 2 others completely did not see the death of the company/idea in front of them. We had majority and dissolved the company.
Do you have paying customers? If so, that's not a bad start. Do your potential customers pay to solve the problem you are trying to solve? That's also not a bad start.
Have you considered hiring a consultant to help solve the problem, or to be the bearer of bad news (not having a clear understanding of your customer or the market)? I've helped people / companies figure out their target customer and what would solve their problems. Feel free to reach me at helpthingchat a.t gmail dot com if you'd like.
As to leaving, you can find the best way to frame it, and then do it. If they're really your friends, they will accept it. If not, who cares what they think?
The startup is about to die and you guys are pointing out the cause of death, googling shit, and already divvying up blame inheritance? Get out there. List your assumptions, meet people, try to get paid, get told your product sucks, get proven right or wrong, repeat.
>I would like to leave, but I don't want to be the one getting blamed, when the company finally goes bust. How can I handle the situation?
Which situation? Leaving or making saving your startup? If you'd like to leave, just leave. Just ask yourself if you've given it a real shot.
This takes time but the key is that all of you as cofounder need to make this a priority. I literally was thinking who the heck is my target customer today and I have been running a bootstrapped company for almost 6 years BUT the point is that you have to constantly refine that as needed.
Honestly, if you cofounders don't understand that it is all about identifying the market and the whole "product market fit" thing, it will be over anyway.
Would this blame matter because of your friendship with your cofounders? Or does their blame affect you in some other way?