Those are examples where they shouldn't be using public cloud in the first place. Should build those services to be local-first.

Using a different, smaller cloud provider doesn't improve reliability (likely makes it worse) if the architecture itself wrong.

It makes credit card transactions risky (offline)

Talking more about some unrelated function taking down the whole system, not advocating for "offline" credit card transactions (is this even a thing these days?). Ex: If the transaction needs to be logged somewhere, it can be built to sync whenever possible rather than blocking all transactions if the central service is down.

Payment processor being down is payment processor being down.

Do any of those competitors actually have meaningfully better uptime?

From a societal level, having everything shut down at once is an issue. But if you only have one POS system targeting only one backend URL (and that backend has to be online for the POS to work) then cloudflare seems like one of the best choices

If the uptime provided by cloudflare isn't enough then the solution isn't a cloudflare competitor, it's the ability to operate offline (which many POS have, including for card purchases) or at least multiple backends with different DNS, CDN, server location etc.

Cash exists, physical tickets exists.

those things shouldn't be fully tied to the internet/intranet anyways.