Besides the roughness of the paper, I found that layering layers of tone with harder pencils (H, H2) helps to even out the tone a lot. Don't press hard, just apply lot of layers very lightly. I use a mechanical pen with H2 lead. It's kind of tedious but very relaxing. Check out some of the videos from/with Stephen Bauman.

First of all, I like what you're doing. Drapery studies are a great tool for work on your drawing fundamentals, be it line quality, composition, or value. You didn't ask for it specifically, but I suggest you bring some more clarity in the values, separating light and shadow, using a core shadow. Make sure anything shadow is darker than anything in the light, play down the details in the shadows, and go for a nice core shadow to separate the two.

Well like others have said it’s a question of surface (smoother paper) and method, like rubbing your tone in, using softer pencils, charcoal dust etc. So at the core of the matter is knowledge and understanding of your materials and their properties so that you use them to your advantage instead of fighting them. Pencils of various types have a range of “looks” opposed to others, or graphite, or charcoal. Add the interaction with the various surfaces and you can find a combination that will give you the range of texture and treatment you want as well as feeling comfortable to you. That is why it’s important to experiment after a while with various materials, to find what is better suited to your temperament and as you become more proficient with them all you will be able to use what is needed, and even better, your temperament will adapt to a wider range of materials over time. That having been said, you can try something that will be more time consuming, but will give the result you’re looking for... when modeling (not “shading” as some say) use the tip of your pencil to slowly fill in tone instead of a stump tip or the side. You will cover less ground but you will be filling in all the nooks and crannies of the surface, making a less noisy or rough texture. I also find that, when done right, this results in a drawing that has more “vibrancy”, a quality of light that sorta seems like it gleams.

In addition to what everyone else said about paper, I've had success with manually filling in the holes kinda like this(although, it's quite tedious): https://www.youtube.com/watch?v=epQhS1cHeCg One of the major artist pencil brands(I think Faber-Castell?) recommends going over your B grade pencils with and HB to fill in a lot of those holes too.

Great job! I recommend using softer graphite pencils on smoother paper or maybe consider using charcoal, especially on rougher paper.

You could try a smoother paper or a blending stump. I haven’t had a ton of luck with a blending stump yet but I know others swear by them,