If you’re chronically ill, you shouldn’t be risking your health by founding a company. Take care of yourself first, you are competing with others that are in tip-top shape.
I am actually speaking from personal experience as an ex-founder with a disability. My disability didn't stop me from founding a company (nor did it stop me from becoming a state championship athlete and being one of the first from my hometown to ever become admitted into a top-10 university), but an unrelated chronic health problem kept me from being as productive as I needed to in order to succeed in business.
A lot of health conditions can be worsened by overwork (remember Sam Altman got scurvy while building Loopt?), and founding a startup is one of the hardest things you could possibly do. I know plenty of otherwise healthy people who ended up damaging themselves while trying to start companies.
To this day, I'm still recovering. Overworking and putting yourself in overly-stressful situations is UNHEALTHY, full stop. I made necessary trade-offs (as any sensible founder would) by eating cheaper food, skipping doctors' visits, cutting back on sleep, falling behind on exercising, and getting bargain basement health insurance. In retrospect, I definitely regret it.
It's a bit offensive to me that you are on here virtue signaling as some champion of anti-able-ism even though you are likely perfectly able yourself.
Regarding your point: That does not sound like an issue inherent to startups, but more like an issue of bad prioritizing. Why does an start-up have to be all-or-nothing? Robert Graham advocates this way of going in, but there are plenty successfull examples of people keeping it low out there too.
Yes, stress is a killer, and startups are often more stressfull than other jobs - but most of the effects of stress depend on how on is dealing with it. And that can be trained.
Competing is a two-way street. If one has enough money banked up and enough motivation, why shouldn't they go forth and found? Chronically ill persons are usually able to do things, and if that thing happens to be a startup, why not?