The smoke looks blur and unclear when rendered

This is the render quality after decreasing the steprate value (watched from Youtube tutorial on how to increase the render quality). But the quality remains the same.

There is a problem with the rendering quality of this smoke fx. 

I change my project to a new one and tried rendering out the shot but the smoke still come out blurry.

And i tried increasing the resolution but the result is still the same.

After adjusting the lighting & switch off the denoise, it becomes better.