Which is still pretty much a bug or rather an error in design, though... Players want to be attacked. Changing the fundamental structure of the game in a way that makes players not get attacked anymore is making the game less of a good game and may need to be seriously reconsidered, and soon... I.e., that's not just a sufficient explanation or justification by itself to say that it has changed.
I'm not saying we go back to making them out of thin air. But you also probably don't want the world to simulate goblins COMPLETELY realistically as in treating you no differently than any other fort. You'll need something in between -- adding parameters in that cause them to bias toward your fort beyond its actual strategic value or the actual chance of stumbling across it.
And you say the populations can't support that. Okay, so up the populations and the gobline breeding rate too so that they can!
Etc. etc. Excuses for a boring game don't make the game fun. Fixing the problem makes a game fun.
If there turns out to be no way to really fix the problem, then the feature should be rolled back, honestly. I don't think this is likely -- I think there are probably lots of ways to make it work with dynamic simulation. But IF there weren't, then it would be rolled back, not just "oh well, the game doesn't do what we want anymore" and give up...
(this is all a bit hyperbolic. It's still a fun game. But just less so.)