I don't disagree with you both , and you should take my remark with a couple of grains of salt.
![Smile :-)](./images/smilies/icon_e_smile.gif)
There is a prototype for everything, but you are right, a collection of oddballs and exceptions doesn't look realistic at all.
The reality for many of us is that we have usually limited space, so running huge trains is something most can only dream off (or do it at a 'club' meet).
At home in my case, I've chosen the subject of a short line, and i will be running mostly short locals, with 'common' car types, loads and locos. Not a collection of oddballs. Even these locals will probably be shorter than I'd like them to be, 8 to 10 cars max, while in real life those trains would easily have 20 to 30 cars, if not more.
Once my layout is complete (or at least the track work and some of the back scenes are finished), I will be able to hide a through freight behind a back scene, that will likely have enough length to warrant 2 or 3 6-axle diesels, and about 15 to 18 fifty foot (box) cars. Not long by any stretch of the imagination, but on a model railroad , it will be a reasonable compromise that can 'pretend' to be a much longer train.
(and for videos, I could of course do as you do Brian, making sure I start filming such that you can't see the last car, while the train sort of chases it's own tail, and look very long)
cheers, Koos