I think it's
The F# major scale.
The first part:
This is referring to:
An F-grade pencil. The HB scale goes from Harder to Blacker (9H, 8H, ..., 2H, H, F, HB, B, 2B, ..., 8B, 9B). The harder the pencil's lead grade, the lighter the mark. The softer the lead, the darker (blacker) the mark.
My previous riddles weren't hard enough,
The pencil is graded on the hardness of the lead.
so I decided to draw from this experience.
Drawing with a pencil.
I didn't want it to be too black,
The pencil isn't in the B section.
so it's half way in-between.
The F rating is an arbitrary letter chosen to mark the midpoint between H and HB.
Is that not fine with you?
"F" is an arbitrary letter. It doesn't stand for "fine", as is often thought.
The Second Part
My style may elicit some pointed comments,
but the answer to my last riddle was a key on the keyboard,
The last riddle was about the letter "K" and letters close to it on the keyboard.
so I wanted to make a big change,
This is a change in scale and involves keys on a piano.
and I hope you rank it highly.
The rank Major in the military, and major vs minor scale.
(Oh, I guess it turned out to be mostly black after all).
The F# major scale on a piano is played with more black keys than white keys.