Or I can fail at a startup and be close to zero five years later, the fact that you aren't homeless and starving and can get another job doesn't mean it wasn't risky, you still wasted a bunch of years compared to slow and steady accumulation.
I've read the majority of millionaires in the US get created like this, working and saving through decades.
You're basically repeating investor kool-aid, because for their model to work, 100 people will fail and 1 succeed, and so they tell you to not worry if you're in the 99.
For me risk is “could go horribly wrong” but the worst case for most startup founders is … get a job?
Yes, you might waste five years (in your words) of income. But that is not a "risk".
A "risk" for me is "this could all go badly wrong". Not having an extra five years of savings is just a fairly straightforward consequence. It's predictably going to happen, I can decide if I want it.
Real risk is "something can go catastrophically wrong". If say you've taken out a huge bank loan to fund the business and you have to declare bankruptcy if it fails, now _that_ is a risk. But nearly every founder I've ever met has taken nothing like that risk.
That's my point, startups are not risky in that sense, for most people, most of the time. It's kinda strange that so many people think they are.