You can sell the business. Or you can put work into automating it and hire someone to manage it.
The point was that it's not "Be Airbnb or have nothing to show for it". You can join YC, aim for the moon, but maybe end up with something pretty decent for your efforts even if you fail at the big one.
The startup mantra is Go big or Go home.
You want alignment with your investors. To even tell them you're tolerable of a lifestyle business would not be alignment with the use of their funds.
Don't confuse temporary state of 'sustainable' with 'going to continue to maintain a lifestyle business'. Many startups are happy to be at a sustainable state while figuring out product / market fit, how to scale, etc - because it gives them a longer runway without having to raise funds.
It'd still be considered a 'failure' from the investors perspective, and again, if aligned correctly - the founders also. One of my favorite quotes from an investor is 'Don't return my money. Return me 10x or fail ($0 return) trying'
It think the "battle" is over owning the "startup" label. Can a lifestyle business be a startup? I personally don't care much, but if you're taking investment, you can't aim for a lifestyle business (as you explain well).
The point was that it's not "Be Airbnb or have nothing to show for it". You can join YC, aim for the moon, but maybe end up with something pretty decent for your efforts even if you fail at the big one.