As someone recently said it here, the difference between software development and marathon is that marathon runners know their destination.
If you started making a task-tracking app, and after all the work for scrum end up building a video game instead, something has gone terribly wrong.
Instead of using an SDLC methodology here, use one of the relevant product frameworks for that, but needless to say, there is a large element of luck here, as finding a PM/F isn't guaranteed.
Usually you use low-tech SDLCs like Scrum/SAFe at the places that already have found PM/F, or those relying on violence (aka "taxation") as their main business model (e.g. military/government/public sector).
The only PM/F Scrum Inc found is how to make bazillions from useless certifications and training.
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[1] Scrum | Dr Jeff Sutherland | Talks at Google
And it's a competitive sport. It might not be healthy, but that's how you win.
A hiker or a marathon runner or a club cyclist not currently at an event have a destination: where they started. But the good stuff happens in the middle, and that’s not necessarily planned out in advance.
Pacing is even more important then because there may be nobody to come bail you out, or it might take hours for them to do so.
Hell, in this analogy even the marathon organizers don't know the destination. Or much care.