How will systemd-boot guess the thoughts of users? Users will tell systemd-boot. As I said, you can use bootctl to select the next boot. Usually, the desired kernel is "the latest". But if you have an opinion, go ahead and type it in to the computer, over SSH or console or whatever.
"I don't want to play nice with others" - Well, I can't help you there, but being interoperable with the best solution sounds like it's beneficial enough just for our own use, and the interoperability is a side benefit.
"User must manually configure" - you're kidding, right? These configuration files are automatically generated and drop into the standard place. It's easier on ourselves, not harder.
"Simple instructions" - apt install linux-image systemd-boot; kernel-install Balbes-ornery /usr/lib/linux/linux-6.1-balbes150 /usr/lib/linux/initrd; bootctl set-default Balbes-ornery