I feel you there. When I first started dipping my toes into Linux at age ~16, I remember the Ubuntu installer asking me all kinds of questions I didn't know the answer to, like "Would you like to repartition your disk?" "Would you like a logical partition or a physical partition?" "What disk would you like to install your bootloader on?" etc. I had no idea how to answer any of these and I just sort of went with the options that sounded safe to me.
It wasn't until several years and versions of Ubuntu later that I decided I wanted to try a different distro and realized how convenient it would have been if I had put /home on its own partition. The whole concept of "you can swap out your OS and leave your files alone" was incomprehensible to me at that point as a lifetime Windows user. Even if it had been the default to split up the partitions, I probably would have set it to stick with just one, because that's how Windows did it.
(Incidentally, I have vivid memories of my grandfather's Windows hard drive, which he had inexplicably partitioned up to at least G:\ and I think L:\. I still don't know why he did this and since he has passed, I probably never will. Our best guess is that it was a habit he picked up from some pre-Windows OS - he was an early tech adopter, but opinionated.)
>all those startup service managers
I haven't used desktop Ubuntu in a while, but after investing some time into grokking Arch and systemd, I'm pretty happy with my idling process list. I'm pretty sure I know what each of them are and how they got there. I'm young enough that I don't miss init, though, so maybe that's just naivete on my part and malicious gluttony on the part of systemd :)