I can accept that as an opinion, but I guess I'm more interested in discussing the ramifications of literary theme as a major component in RPG campaigns, similar to how plot seems to be a major component in a lot of games.
I think you've already noted that "literary" themes are rather strongly in the hands of the player, rather than the GM.
For example, consider "redemption" as a theme. The GM cannot force that theme. The player must choose to have a character, either in-game or in backstory, do bad things and have a desire to redeem themselves. The player probably needs GM assistance to explore the theme, but the player has to accept the theme.
I'm wondering if a strong theme from the start would allow people to "latch onto" something, and build these interactions better.
It might, with some groups.
One issue you'll hit is much the same as with genre themes - maybe the player's not so into that particular theme to begin with. I'm not going to be a great player for a "PIRATES!!!" game if I'm not really into pirates. Same goes for any other theme.
Also, if you set a strong theme to start with, you will probably tend to work with blinders on, and fail to notice themes that are emerging organically in play that you could take advantage of. If one character has themes of "Humanity" and another of "Redemption" you can have a synergy that would be different than if they both had "Humanity".
I think this is one reason why genre-themes may be more successful for RPGs. With a genre come some standard literary themes that are commonly successfully explored in the genre. Players will tend to pick them up, and you have some assurance the combinations will work out well.
So, I think setting strong literary themes at start less a, "good GMs should do this," and more a, "This is a technique you might want to try on occasion."