Root can be useful for plenty of reasons: there are many apps which use root access to increase privacy, customize the system, restrict apps, manage battery charging, enforce firewall for apps and system, block trackers, backup the system, etc… I currently have 8 apps (if I don’t count all the lsposed modules) using the root privileges to do all of that but I also use it for other things like automation.
The only kind of security I want to have is privacy from my own apps installed on my system, something root privilege allow me to have. For the rest, I just don’t install any random program on my phone and I didn’t have any problem for years.
(and no, I can’t do any of that with shizuku or adb)