Some of the distros are very good, but some of us who have work to do cringe at the thought of bringing up newer versions of an OS just to check all the things that've broken and changed needlessly.
There were other choices that Linux could have taken rather than sysvinit vs init.d and some distros through the years have taken different approaches. FreeBSD's rc.d is not sysvinit either.
I don't think that is true. If you look at those other distros you'll mostly find that it either didn't pan out, or it's quickly approaching the same design and architecture of systemd, where distros start using declarative prgramming to integrate tooling around common workflows. This is inevitable when you consider the constraints on the system as a whole. Other related service management tools like Docker are under the same constraints and you'll notice those have a similar architecture too.
for instance, the systems better checks all memory banks and disks before it finishes booting.
Having a system boot slower is an annoynance when downtime occurs, but having a system boot incorrectly is far worse.
I've run a lot of Linux machines on a lot of hardware for a lot of years and have no idea what could have been going on that would cause a 5+ minute boot, that was also unnecessary enough that a different BIOS could get it down to 30s. Back in the bad old days of circa ~2000 when I ran Linux on a variety of garage-sale potatoes, I don't think any took 5 minutes to boot.