I don't think it's a buggy piece of junk, but I don't think it's close to perfection either, the truth is actually about halfway between if you look at it dispassionately.
I'm happy that the multiplayer system is working as we intend.
In one hypothetical ideal world, all possible content would be built-in, there would not be any need for content creation since all the content would already be available, and so you would never need to download anything. I think we can agree that this would give a better multiplayer experience. However, we don't live in that world and so we need to handle downloading content and ensuring that all participants end up with an equal and fair multiplayer gameplay experience. There are many different techniques for this, each with their own tradeoffs (how much chance of failure? how much flexibility when it comes to content creation? how much protection against cheating? how many manual steps? how much bandwidth will it use? how long do you have to wait? what do we do about copyrighted materials? etc.)
Since we already have a single official repository of free content, which we have the right to redistribute, we have selected a model where all necessary multiplayer content is automatically sourced from the DLS. It reduces end-user interaction to a single click (barring any faults elsewhere.)
It has the upsides of:
* The user doesn't have to worry about where to find content, or which version to use, or whether it's compatible with other users' versions of the content.
* The user doesn't have to worry about whether the content can legally be downloaded.
It has the downsides of:
* Not allowing the use of content which is not licensed for DLS distribution.
* Expecting the user to have a suitable internet connection such that they are happy to let Trainz download the necessary content.
* The DLS interfaces (website, CM, etc) don't always present a clear picture of whether a given route/session will work on your version of Trainz. This isn't a problem specific to multiplayer, but it's something that is appearing in your criticisms above so I'll list it here.
I'm sure you can add a few more details on each side of the argument, but that's the way we look at it.
I agree that it doesn't necessarily achieve everything that everyone might possibly want. But it achieves what we want.
kind regards,
chris