TL;DR
I’d advise you to automate backups as incremental daily backups, automate reflector, clearing paccache and rebuilding initramfs/grub config.

1. My system automatically backups at 4 am or boot time anyway, with basically the same command as you (also excluding games, caches 'n stuff).
2. yay -Pw should show you unread news.
3. reflector can be run as a systemd service
4. For me, the journal never grew to a large size, despite not being cleared for any of my systems. Also useful for checking logs on systems where some errors may stay undetected for weeks, like servers (which I do run, successfully, without problems at all, on Arch testing repos. Even arch for arm works without any problems at all).
5. There’s a pacman hook in the AUR that automatically clears the cache to the last three versions, or what you want. Despite that, my yay cache is ~60 GB, which is more than the rest of my system combined. Still not an issue, as it is excluded for backups and I can just clear it or change the limit.
6. As yay basically just invokes pacman -Syu, that step is actually pretty redundant.
7. Errors should be outputted at runtime of pacman/yay, so as long as you don’t have 200 pkgs to update you could monitor normal and AUR packages at once.
8. If packages are removed from dependencies they should be uninstalled automatically I believe and using pacman -Rs should remove packages that were only installed for the package you are removing. (Btw, -n removes config files too, if you don’t want them anymore). Despite that, I do check for orphans etc. when I feel like I want to clean my system(s).
9. Just yay upgrades AUR and pacman pkgs, as said in 6.
10. Just as 8, orphans shouldn’t happen anyway. Though I did not know about the AUR specific command, thank you!
11. As I’m, not even joking, updating and “newest software” addicted, rebooting every time is very annoying, especially for servers. Luckily, as I update extremely often, it’s often very few packages so I can quickly decide if to reboot or not. In general, packages like screen or python can be ignored. Packages like sshd can be reloaded by just restarting the service (systemctl restart sshd). Only kernel, CPU-ucodes and drivers are a real update trigger for me.
12. I don’t have flatpaks, and eg. pip is redundant as my python packages are managed by pacman/yay. So it’s just yay to worry about.

Also, you missed a little but important step: Recompiling initramfs and the grub config (If you use grub, that is). If so, there’s also a hook for that.

Of course, just automating everything screams for error and system crashes - if not checked. I’d also advise you to check systemctl status regularly, as it can inform you of failed (critical) services, like backups, DynDNS or just shadow.service informing you there’s a user missing/extra in /etc/shadow (which is the password file, btw).

In conclusion, many things could be done as service automatically, are redundant or could be done less often. Though I must say, it is better to do everything explicitly and with care, like you do, than to skip over things.