The point is that list isn't first-in-first-out. Public waiting lists are constantly reviewed by domain medical expert committees in the public system to triage priority patients.

If you're truly urgent, you will get bumped up. If you're not urgent, you can get bumped down as others go above you.

Unfortunately, individual QoL and urgency can sometimes be disconnected, which is why pensioners getting hip replacements can get bumped down despite having loss of mobility due to heaps of pain.

Cumulatively for lots of non-urgent activities (diagnosis tests etc) that drag can add up.

Much like any commons, is no perfect system, funnily enough.