I completely understand your concerns of thinking rarity should still be a thing, and you would like to have a collection to be proud of that includes very rare items.
I have quite the collection myself, but the extreme rarity of things should not be at the point where "underground markets" are making thousands off these sets. It's quite ridiculous. The developers need to address this issue.
Overall, this is suppose to be a game where your account should only have sentimental value, & not actual IRL value to begin with.
This suggestion is gold and you are absolutely correct! Everything should be (reasonably) accessible to all and we are lucky because the game is going in that direction. I'm sure they will bring back these and every other gameplay along with gem promos and tropical beaches. We just need to keep suggesting and when they have the time they will grant it