It's not harder, it's basically just not going to happen. There's no way to do this challenge from scratch without spending cash on buildings or kits.
I started from scratch (guess I had a couple dozen whistles and tags already) and didn’t build my main stage for 3-4 days. I’m one item from finishing.
We’ve all been there with the drops. Given all the events recently I’ve finished in 2-3 days I’m glad this one is a hit kore challenging.