I will try to express this in numbers instead of speculation.
After the doubloons changes I have done 126 islands, if I consider getting doubloons as nothing, 43 of these runs dropped something, that is roughly an 34% chance to get an item other than coins.
Now, if I go and check the amount of times I have gotten nothing in 126 islands before they applied the 100% bags drop rate, I get I got 77 times out of 126, for a 61% chance of getting something.
If I consider the total amount of islands instead of only 126 runs, I have 102 islands rewarding nothing and 203 dropping at least a bag, which is pretty much a 66% of getting loot, which is pretty close to the previous sample.
Not only that, the chance of getting more than one addition items seems to be much lower too. Before the changes I got 3+ items 8 times, after the changes I have seen it happen only 3 times (comparing 126 with 126 here, not the 305 sample).
So yeah, it is obvious they changed something. Even heroic islands feel like crap these days.