I'm like 60% done with my island and I love every part of my island, and have already used my design slots as efficiently as possible, and time travel excessively. 1000+ hours and I can't find myself coming back to the game until they add more design slots. I just don't see how 50 is enough for...
Maybe at 4 stars for me, but I quit a few months ago.
Still waiting for more design slots, until then I feel like there's nothing else I can really add to my island without removing anything first :\