I'm pretty sure that if I was to begin using Trainz for the first time , this year, , I'd give up , not only is the purchase far more confusing , with so many options, but there seem more defective assets and items that do not work as they used to back in the old days.
I understand what you are saying and yes, there can be a lot of confusion/frustration in Trainz, more than perhaps there should be.
Now I do not have a very broad experience with video games, but to me the big plus in Trainz is its community involvement. How many simulation games are there that allow ordinary users (not computer geeks/nerds/programmers/etc) to create content for the platform? I am certain that there would be others but from what I have heard the creation experience is often not great. They can be great at running, trouble-free, worlds or whatever that have been created by the programmers or those creators who are in the "inner circle" but not by the average "Casey Jones" user.
The fact that I can easily create my own complete and complex railway worlds is the "wow factor" that keeps me with Trainz, and keeps me updating whenever a new version is released.
I doubt that I will ever master Blender (no matter how many times others tell me it is easy) so I happily restrict myself to creating assets that are not 3D.
From your timeline you were not around in the early days of Trainz (1.3, TRS2004, TRS2006 and arguably upto and including TS2010 and even TS12) when there was a lot of very "sloppily created" content from users who did not follow the rules (as slack or "forgiving" as the content creation rules often were in the early days). These assets, enthusiastically and generously uploaded to the DLS (and I am not knocking those creators) caused a lot of problems, far worse (IMHO) than we see today.
I don't see any confusion over purchases. I will admit that I was initially confused after purchasing the subscription and finding that my TRS19 Platinum Edition was suddenly renamed Trainz Plus on the top of the screen window without any download, and more recently, renamed to TRS22. But that conclusion was quickly cleared up.
The latest newsletter contains information about a simplification of the types of memberships and purchases that can be made.
As you noted, the community of users is one of the greatest strengths and assets (not on the DLS) of Trainz.
My opinions.