Discuss Cron: Alternatives? Uses?

So I looked in to "cron" a while ago, and am looking in to it again:

The software utility Cron is a time-based job scheduler in Unix-like computer operating systems.

Immediately one problem is cron won't execute if a system is down, so this isn't suitable for computers people turn on and off, or some workaround is needed for that case. I have not been able to figure out what the best workaround is. I did see there were some "asynchronous" programs that could execute if/when the computer boots back up, but they started to seem more complex or with complicated syntaxes. I'm literally just asking for a simple "time / program to execute" format.

This seems like a really simple issue, I basically want to set a bunch of alarms to execute programs when they go off: some recurring, some one time alarms.

In researching this, I found a multiplicity of complicated systems all over the place, I'm still not sure if any do what I'm looking for or what workaround would be best.

There is an "at" command for one time execution of tasks... but why does it have to split in to "cron" for recurring tasks, and "at" for one time tasks, why can't they just be one program that specifies if a task is a one time program or recurring, and can execute code upon a reboot?

So I've been stuck with something of a "manual cron" system where I just try to remember to manually execute commands on a written schedule... so far I'm not sure if anything is more efficient.

Or basically like "Tasker" on Android, which seems to run "tasks" on a schedule?

Or should I just create a ton of "at" jobs that repeat? That seems like a bloated approach but would work?

Create a program that checks time and executes commands if it is past that time and just remember to run it frequently?

I admit that I feel like I am reinventing the wheel and am somehow needlessly complicating things, however I have seen a variety of cron-like projects and reimplmentations that seem to indicate that something is amiss in this discussion.

Also, what would you like to use cron for? This was another puzzling question, a ton of links were on how to code cron but not really discussing what people want to use it for (I saw a lot of similar ideas discussed with use of "Tasker" that seemed helpful to this end).

Has anyone figured out or solved this issue for themselves?