I agree that some goals may be time dependent. However, it does not follow that ALL goals will be time dependent. I would go so far as to argue that many goals aren't. "Become the greatest swordsman" is not time dependent. "Become king" is not time dependent. "Become a god" is not time dependent. Other than doing it before you die I suppose.
Those all take time to achieve, and any time spent not trying to achieve them decreases the chance of achieving them.
They're all time-dependent.
What does this have to do with Raven Crowking's example? In his example, it's not "slowly replacing"; it's rapidly slaughtering.
10 people a day is VERY slow for a kingdom, slowly replacing for a kingdom >>>>>> rapidly slaughtering for an individual
AND, there's the bit that you've ignored. In RC's campaign, you deal with this now or, if you let it go, it will be much, much more difficult later.
That's how life works, isn't it? Stitch in time and all that?
How is punishing your players for not following your storylines not textbook railroading?
Giving them a challenge which increases with their level, so they can face it when they wish, and giving them a downside to not facing it now?
That's not railroading, that's just building plothooks realistically, and with fun in mind.
And, again, how is this a resource for the PLAYERS? In RC's example, you either put off any of your personal goals to stop the ongoing plot, or you get whacked with a big old punishment stick.
Because the players can spend their time preventing that punishment, or they can spend it achieving their own ends.
If a world has tax-collectors, does that make money not a player resource, because they need to spend some of it on (avoiding) tax?
Even in your example, if I, as a player, decide to pursue a personal goal and put off dealing with your dragon, I get smacked with the big old punishment stick because the dragon now has a much larger force than it did before.
That's a realistic outcome, is it not?
The only alternative is that ALL plothooks are static "there's a dungeon here. It's not doing anything, no-one is being harmed, at all, but there might be some cool stuff down there"
Which is rather limiting, don't you think?