Wolfram stout
Hero
Sure, they may be fun to read for pleasure. I personally find the Silmarillion pretty boring overall. But opinions on that will vary by taste. And, reading is (almost always) a solo activity. If someone is reading something and they decide they don’t like it, there’s no harm in simply not reading any further.
But… think of it as a game. If LotR was an RPG, almost none of the Silmarillion is needed for play. None of it actually matters. The “players” never actually interact with any of it.
It’s the kind of self indulgence that I think is among the worst traits a GM can have (and trust me, I include myself in that).
So, I think that the Tolkien = GM, Readers = Players, and Silmarillion is a workable analogy.The GM has to have fun too. They don't work for the players, after all, and their fun doesn't become bad/wrong when it isn't all about serving their needs.
That said, the Silmarillion didn't make it into play. For original readers, they didn't get that world lore until decades after the "campaign" ended.
So in a sense Silmarillion was the GM having his fun, and only a few players having much interest in "all that lore stuff". And that's all good.
With my players (not that we ever play anymore grrr) the Star Wars crawl is about all they digest for either fantasy or sci-fi campaigns.