Obviously processor resources (CPU, memory, hdd) affect render time. But 9 minutes - one clip, with a title and a 15 second scroll on a second video track, takes an hour to render in 1080 low res "quick and dirty" format. The final piece runs 24 minutes and takes almost 12 hours to render in 4K 59.94 fps. Putting together a longer video, at this pace, isn't worth considering.

As it is, trying to position the head, in the 9 minute piece, takes 5+ minutes from the time the next location is clicked on to the point where the head moves to that point.

Playback is non-existent.

What's going on here? Is there something I'm missing?

You could try to enable proxy clips. This will make editing much more responsive. Rendering will stay as it is, though.

I'm just waking up to the proxy concept. I'll look into that.

My current project, expected to need 8-10 hrs to render in 4K, involves a number of transitions and other effects, on a number of tracks. My next projects (all documenting 15-45 minute rides on specific Alpine roads) will have simple transitions (watching me read a map or hit the GPS gets old fast - cross dissolve...), but still wind up in the 10-30 minute range. Anything to make the process less than glacial is a big plus.

I guess you're still on Windows? This port still has very few users, maybe the MLT build options should be optimized...
On Linux you would be in a better known world (from Kdenlive community point of view of course!).
GPU processing for example is not ported to windows yet, however even on linux it is a bit buggy, I usually disable it :\

Yet 4K@60fps is very demanding, using proxy clips for editing is almost unavoidable.
Rendering in HD (1080) is usually not much slower that realtime or half realtime on my i5, depending on output codec (H264/265 encoding can eat up most of the power, for quick preview I have custom MJPG or DNxHD profiles) but also on effects used (color adjustments can drop render speed by factor of 10!).
Title clips used to be so buggy few years back that I learned to avoid them (using PNG/SVG titles), I'm not sure if this is still a problem.

I use Win10 mainly because of annoying Linux issues. I've used Linux, off and on, since the pre-V1.0 era, but the current round of choosing between OpenSUSE, [/U|K]buntu Vnn.nn [/MATE|KDE|Gnome] is slowing me, to say nothing of porting, and re-organizing 400+ Gb of video.

Probably time to pull up my big-boy pants, settle on something for the machine, and start porting. [/grin]