Yes, true, jallan, other works well pre-date The
Hobbit.
Middle Earth was first mooted in discussions between the TCBS in Sarehole, and if we're going to look for the true 'first leaf' in time, we can even go back to the "green great
dragon".
However, my impression was not based on the first seeds in
time but in the first fruits of publication. Your above post is well considered and valid, and I wholeheartedly agree with it. What I'm posting is the
impression I gained while reading the story, and it was of the published history, not the chronology of the birth of
Tolkien's stories - a personal interpretation, but I readily admit that it is not the only valid one.
The
published success began with The Hobbit, then LotR. Other publications were of minor public interest, and would never have made much money (I would class these works as the small canvases, tacked on to the edge, being not of Middle Earth).
Tolkien said the Hobbit was never meant to fit, but he also admitted that it did, and became, in fact, a major cog in the story (making him ever regret the 'childish' language used in its writing). I call it the first leaf not because it was written first, but because it was published first - and thus became the appetiser for LotR - the clamoured-for sequel. These two
books are the ones that became the world that spoke into the hearts of millions of people and (in the words of Voice one and Voice two) made their purgatorial experience so purging of life's negative influences. Tolkien's other writings had less effect, except for those who took the further walk into
the Silmarillion (the distant
mountains in LbN).
It is true that LotR was Tolkien's bread and butter after his retirement (though Merton took over after Edith died), but he never really had the leisure that a successful author might have hoped for. Before he retired, University work was ever snapping at his heels and poor health (his own or Ediths) was ever a problem.
After retirement Tolkien still found life intruding on art - writing ever shorter letters to unknown correspondents so he could get on with the Silmarillion (the distant lands), with health and home problems ever present and, even then, never finishing it to his satisfaction.
In Leaf by Niggle, the success of the canvas was in its true realisation after Niggle's 'journey'. Tolkien's work, far from being ignored, has had pre-purgatorial success in
this world. I think it was tacked to Parish's roof (in particular) because he represents those people who ignore faerie and dismiss it as irrelevant. In LbN, this prevented the work from being appreciated by anyone else, but in real life, of course, Tolkien's works
were published, but the Parishes of this world still exist, and still ignore faerie to their spiritual poverty.
In the end, only the leaf remained, and even that passed, as all things must. We cannot envisage a time when Tolkien's work is not available, but we cannot see all things. The
tales of destruction in ME's history show Tolkien's thinking on those things that appear to be permanent. The leaf may yet pass into forgotten history, along with Niggle.
I am viewing this story from a different viewpoint from you, jallan; and I hope I've finally managed to convey what I'm getting at (a gift that often evades me).