Many people think it is - but the realitiy is that it depends a lot on the system one is working on, can be super tricky, and often relying on it will cause some pain points later on.
e.g. let's take the example of an init system starting up all processes. Now what happens if a if one of the processes crashes and gets restarted by a processmanager? Now the order already changed, and e.g. a former process which relied on the restarted one might work based on outdated data. Similar things can also happen on other layers - e.g. one of the services in a dependency chain might disappear and reappear.
Another example is a developer/administrator manually changing the config of a certain service and restarting it to take effect - that could also trigger dependency problems.
Now those are absolutely solvable - either by making sure all services operate gracefully with any startup order or by other mitigations (e.g. "always reboot the full box"). But like everything else in the list, it still is a problem that is observed in very often in distributed systems.
e.g. let's take the example of an init system starting up all processes. Now what happens if a if one of the processes crashes and gets restarted by a processmanager? Now the order already changed, and e.g. a former process which relied on the restarted one might work based on outdated data. Similar things can also happen on other layers - e.g. one of the services in a dependency chain might disappear and reappear.
Another example is a developer/administrator manually changing the config of a certain service and restarting it to take effect - that could also trigger dependency problems.
Now those are absolutely solvable - either by making sure all services operate gracefully with any startup order or by other mitigations (e.g. "always reboot the full box"). But like everything else in the list, it still is a problem that is observed in very often in distributed systems.