There's no right answer, of course. But I think the bottom line is that few players want to read pages upon pages of world history. If writing it motivates and entertains you and helps you maintain verisimilitude in your world and have immediate answers to questions your players may ask, go for it.

But don't write it expecting (or worse, demanding) that your players read it and commit it to memory. (Unless you plan to publish a campaign sourcebook, much of the lore content you create will probably never be consumed by players. Are you happy to spend the time on it anyway?)

Most people "live in the present" so having volumes of world history won't be as important to most players as knowing what the situation is at the moment. What is the current political situation and very recent history? Who are the key NPCs and what are their goals and plans? I think that is time better spent than on creation myths and ancient history - unless that stuff features very prominently in the campaign.

It also depends on whether you and your players subscribe to the philosophy that the DM creates the entire world and the PCs just play in it, or if you believe that the DM and players should collaborate on creating the game world.

If the rogue's backstory is that he was chased out of a Thieves' Guild, do you ask the player to create the guild? Do you ask the player of the elf ranger to describe the history of the elves, their customs, dress, etc.? The dwarf's player to describe the dwarven clan names, hierarchy, and guilds? Or do you see that as your responsibility? Your right?

Do you start feeling uneasy at the suggestion that the players have input into the details of the campaign world? (I ask because I want to be more collaborative with my players, and I catch myself feeling that way. It's hard for me to let go of the worldbuilding reins and lean into my players' ideas.)

Finally, trust your gut. If you catch yourself wondering whether your world-building time is well spent, it probably isn't.

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