I hope you chaps will not mind a point of view from London England.
The 0 Gauge scene here is some decades behind the USA so far a development is concerned but it's now accellerating well.
There are now a handful of brass importers so 0 Gauge modelling is finally turning from kits to ready to run-so-far as scale (1/43.5!) goes. Cars (carriages) and trucks (wagons) are also becoming available ready to run. This applies to the "finescale" end.
When it comes to tinplate, our version of Lionel was Hornby, but there were several other firms active before WW2; after WW2, apart from some small 0-4-0 clockwork Hornby trains, and miniscule production from the others, the entire hobby went for 00, prompted by the resumed production of the world-beating Hornby Dublo system - which introduced the world to 12v dc, by the way. Introduced in 1938, it was objectively better than anything available in commercial quantities in any scale - and it took up a quarter of the space. This was overwhelmingly important after WW2 when Goering &c had done their best to demolish as many homes as possible. For the great majority, space was tight here.
You will all know about "Century of Model Trains" by Allen Levy, the inspiring book from c1975. For the last 15 years we have had Allen Levy's ACE trains (there are now some others too) and the way the ACE range has developed is instructive.
ACE started by reproducing accurate versions of scarce Hornby locos, though with electric drive, but have morphed into doing their own, improved, versions of what the old makers might have developed should 0 Gauge have prospered here after the War. This has resulted, not surprisingly, in the 0 Gauge version of Hornby-Dublo trains in some cases - popular prototypes then are still popular now!
With exceptions, there is no great shortage of the old stuff since the number of people following tinplate seems to be falling, with many Estate-sales occuring each year. The new production, therefore, adds to the scope of what one may incorporate into one's collection.
It also has the effect of democratising the hobby, since one can now get for about $1,000 a better version of a pre-war Bassett-Lowwke streamliner which otherwise would cost $15,000 - $30,000. Yes, of course, it is thrilling to own one of the originals, but often only a few dozen were made (their recurrence in the catalogues is highly misleading - they were there to pad-out the range, giving the illusion of large production).
So, the slavish copying of the old stuff is being avoided in modern times, and the variety of trains available to all is rising. There is nothing to dislike about that.