I actually wrote a post about coming up with ideas, and the difficulty of doing so before:
https://www.lifehack.org/articles/productivity/how-to-consis...
There are two things you need for ideas:
1. The raw material from which to generate them: Other older ideas.
2. A mind that is able to synthesize ideas appropriately.
Ideas becoming 'harder' to 'find', is simply a function of one of these two things not being fully optimized.
I personally don't think that we have less of either of the two.
So no, I don't think Ideas are getting harder to find.