In my experience, timeline advances make settings unplayable.
Something interesting is happening in the world that involves important people and factions. I would love using those ideas in my game, but I know there will be another timeline update in a few months, and whatever I do to the NPCs and places in my campaign will be different than what the new official timeline update says happens. So I have to wait for the next update before I can plan my campaign. But then I know there will be another timeline update some more months down the line, and I first have to wait for that to come out before I can actually start planning my campaign.
There never will be a good point to start a campaign that deals with major developments in the world until we have the full story complete. That's not producing game content, that's producing fiction dressed up as game content.
The only good way to still actually run a campaign and not running into the next timeline update making everything invalid is to prepare campaigns that won't touch on the ongoing big events in any way. At which point it again is not game content but tangentially related spinoff fiction.
That's why I actually sort of like where the Forgotten Realms has ended up (at least for now): there's a ton of canon, but it's almost all in the past, and it's mostly up to you whether it might have changed in the interim; and the timeline does still advance, but glacially, nonlinearly, and often (though not always) vaguely enough, indeterminately enough, and modularly enough so as to give DMs a lot of latitude to tweak things without ever contradicting anything that's released later. (Both the movie and any potential 5e FRCS would nullify this virtue.)
At the same time, I've always thought the complaint you register, while a valid concern and one that I share, is still a problem with non-metaplot, frozen-timeline settings. Take Eberron, for example: the timeline hasn't advanced, but new products have been released that provide additional, canonical information about areas, organizations, characters, and even past events that were less fleshed out before (including Rising from the Last War). If you've run an Eberron game for any length of time, presumably at some point you've had to fill in details about some area of the lore, and then at some later point a new book got released that filled in the same area with different details from the ones you invented.
The only settings completely free from this problem are your own homebrew settings, or "complete" published settings for which no new lore details will ever be published. Freezing the official timeline mitigates the problem, but it doesn't eliminate it.