Why can't I render sharp images? I can't seem to output sharp images.

I've search everywhere on the internet but the only solution I've found was to bump the samples but that didn't solve anything.
These are 1k samples with Intel's Denoise and 5k samples examples.

1K samples:



5K samples:



Here is the blend file 

Can anyone help me please?
This is a result of too low render resolution.

1000px is just too low, and upscaling makes it look blurry.
Render the image at 2000x2000px instead, and even with just 200 samples you'll get nice sharp edges (just tested it).

Bonus: How to properly connect the Denoise node for best results :).