Founding a genre like a boss
Stealing everything possible from mythology and the, maybe sometimes a tiny bit boring, old, classics.
The beloved tradition of using others' ideas to create something new is big here, especially because Tolkien had the perfect background to milk everything from wherever he could find inspirations, from ancient to medieval and, at the time, modern works. It would especially be interesting to read or reread LotR with a focus on how he let the classics mutate to new forms, transformed oldfashioned tropes to fit for a modern audience, and especially made it a compelling, well written, and suspenseful pageturner. Don´t be angry, good old classics, it´s not your fault, your poor creators just had no creative writing courses available or were hunted by the inquisition, or it were total monopolies to that their works were the only ones available, and thereby never cared about royalties, book signing tours, or target audiences.
Black, white, and the most important grey
The pure, camouflages fascistic, evil, is of course as noir as possible, but especially the sexy seductiveness of the mind penetrating psi magic of the distilled badassery, is one of the main driving engines of the groundbreaking epic journey, because good old almightiness totally corrupts. It´s just normal that everyone is struggling with the whispering of the dark side with all its attractive options and the real life implications of this are, well, terrible, frustrating, and daunting. Throw money at close to everyone and she/he will get corrupted, especially if the alternative is to get eaten by orcs while the family is slaughtered by Uruk hais and Balrogs.
Establishing cliffhangery ends of single parts
One just can´t stop, this damn, evil tendency of the genre to stop at the most suspenseful part and let the reader hanging to wait for felt eternities. As if Sauron wasn´t bad enough, this vicious cycle continues with each new, far too multi k page series and eats away the lives of poor, innocent humans, not to speak of their tormented souls that can´t find peace over these nauseating periods of despair and regret to have been relapsing. Again! I´m not sure if Tolkien should be praised or damned for having laid the foundations for things like Sandersons´, Jordans´, Eriksons´, etc. amazingly exhausting and immersive monster series. I´m ashamed to admit it, but I have the whole, good old second hand paperback, Wheel of time series ‚(and the new ones) lying around and I am afraid to restart reading the whole thing (not just the first few parts like a few years ago), because I fear that it could trigger reading and rereading other series and finally Wheel of time again until 2027 or something, not just having lost contact to reality (not much difference to the present reality, but, much more problematic, to all other genres for half a decade or something. Thanks for that, J.R.R!
Being attacked by the bigoted academic society of the time
That´s just ridiculous, Tolkien had to hide and vindicate his amazing work, because it wasn´t highbrow enough for his snobbish, elitist, and old, boring, so called quality literature prone, colleagues and a bigoted, conservative society that wasn´t ready for something new. Better stay with theater texts as books or whatever can be used for patriotic „our writer“ idiocy. Just bad luck that there aren´t enough good, if any, old writers for each country to fuel feelings of literary supremacy. However, it´s one more of these examples of how parochial even seemingly well educated and sophisticated people can be as soon as it comes to close to their cognitive dissonances and socioeconomic status hierarchy overkill.
Putting in meta, connotations, and social criticism
Tolkien was heavily influenced and inspired by war, and the atrocities humans so much love to do to each other until nasty nukes eliminated the option of more WW action, and put the real life implications everywhere in his work. Not just in the form of the big, bad government cooperating with war industry, propaganda machines, and black magic, but with
Corrupted blood
The banality of evil, the attractiveness of the dark side is, as mentioned in „Black, white, and…“ above, is one of the driving forces of the saga and without Tolkiens´experiences, it might have stayed much more superficial and have never reached that deep level of human soul and psyche vivisection. The same with love, without his lifelong, deep bound to this adored wife, he wasn´t allowed to see until reaching full age, the importance of emotions maybe wouldn´t have unfolded and played such an essential role in the work. Expanding this whole, philosophical, psychological somewhat assumptions to his profession as a philologist and, for the standards of the time, mad professor, would go a bit too far, but let´s just say that his expertise might have helped him create both Silmarillion and Lord of the Rings.
Is it outdated?
Very objective thing, even if not including the sociocultural, immense literary impact, Tolkien invested a bit more than the usual fantasy writer in her/his third or fourth series with a new one each new year. Just take the mentioned Silmarillion, the immense details of the world, all the links to the cultural heritage, and the sheer scale and size, and, on top of that, close to everyone agrees that it´s a timeless, genre founding, ingenious masterpiece that will stand the test of not just time, but eternity. Sure, it´s not as accessible as the average, new, overhyped world bestseller, but that´s the same as with Lem, Lovecraft, etc., authors just were used to write in that wacky, overcomplicated, intricate, and difficult to digest language, because they were no narcissistic, lazy, self aggrandizing, god complexed hedonists. I won´t excuse for that, I´m one myself and get a free pass because I said so first.
Comparing and contrasting fantasy with other genres
Horror, Sci-Fi, or crime had no similar big bangs (fringe theory, by the way, to provoke and insult even more additional people than with just the human degeneration gag above lol) but different founders, prodigies, and subgenres, while fantasy was, stayed, and will be very genre compliant, not to say a bit inflexible in contrast to other genres with much vaster differences, especially sci fi, my bread and peanut butter. So one could say that close to every, no matter if grimdark, YA, high, epic, romantic, etc. fantasy, is always quite the same with some variations of magic systems, the balance of focus on protagonists or antagonists, tone, and the rare establishment of the one or other sub sub genre.
The endless evolution
Close to all human mythology, faith, myths, etc. is fantasy and I see one of its biggest potentials in a fusion to science fantasy, because it opens up all options including any horror or psychothriller crime plot. Without Tolkien, this amazing development couldn´t have taken place so soon and it would have probably needed much longer to establish the (I´m a sci-fi head, sorry) second best genre to subjugate and enslave them all.