The first thing I would advise is to be as transparent as possible with the founder, you can't go on like this. Don't go in as the whole team, it'll probably be a hard time for him, you need to break the news but let him time to digest before going into the details. Keep in mind without him you probably won't be working together on this great product.

I see 3 probable outcomes:

- he does not see the situation as you do, but does not want to leave. this would make leaving the company easier for you if your disagreement is too profound.

- he understands the misalignment won't be solve and quit (either by choice or following investors pressure)

- he agrees to try to change things, this will be hard because it won't happen instantly. Your team will need to set checkpoints with dates, which if not met bring you back to the start.

Anyway for your own mental state (and your teammates) you cannot go on like this.