I fully understand where you are coming from and in an ideal world all software would be "finished" (barring undiscovered "glitches" and the like) before it is released and in some software areas this is certainly the case. But in the world of gaming software, where you publish by the deadline or you perish, the commercial pressures to get the product out "ready or not" are enormous. Train simulator "games" are a very small niche market with several competing products. While companies like EA (for example), which seems to have the NBA gaming franchise sown up, can afford to delay their releases to get the "surface polish" perfect, this is not true of smaller single product operations.
You're right: larger companies with more control of their respective markets can afford to delay their games for the sake of added polish. Despite some companies not doing that to begin with, i don't think this excludes N3V from this equation. T:ANE was a buggy mess on Day 1, similar to something like, say, No Man's Sky. T:ANE needed extensive bug-fixing, optimization, and overall improvements to get the game to function on a large chunk computers, and i think that could've been avoided.
When it comes to Trainz, i don't think most of the community would have minded if N3V had pushed the release for T:ANE back a few months of even a year if it meant getting a "finished" game. The only people i think that would've cried out would have been young children, but i can't say for sure. Trainz has a really dedicated fanbase, for better or worse, and i think that this dedication would've allowed N3V to delay T:ANE for the sake of bringing it up to snuff.
I know waiting for free updates isn't nearly as bad as having to pay for them (ahem, ahem, Railworks, ahem, ahem), but T:ANE, even in it's name, was told to be the "New Era" of train simulation; the fact that the product we received needed over a year of extra development after its release just for the game to be considered stable leaves a bad taste in my mouth.
Personally, it generally does not worry me if TANE (or TRS2019) has "teething" problems on its release, as long as they get the serious issues fixed. The SPs and HFs do not cost us anything except some time.
TRS2019 looks really promising. I do hope N3V learns their lesson from T:ANE and gives the community a functional game on Day 1 though, instead of making us wait a few years for the "true" experience. I'd rather wait a few extra months for a technically-finished product then get a game that's unfinished, buggy, and poorly-optimized, like so many games are nowadays. Extra development time can do wonders for a new product.