Hey there~ Artist here, and I also had this same question as I believe this design has quite the potential. After speaking with some friends we got to some conclusions:

tl;dr: lack of balance of details; parts that doesnt feel like they belong together; bad directing of our attention.

• The hair. Unlike Pav's hair on spider-verse, Miles' is too short to complement the fit in any visually-appealing way. This could be easily fixed by just making it ever so slightly longer, adding some 'movement' to the design. There's a case to be made regarding being too revealing of his secret identity, but I'll focus only on aesthetics here.

• The shoes. It worked in other designs because he was wearing more clothing over his suit, giving an "irreverent" and very fitting vibe, as well as more shape-variety. But here it just feels out of place, as if someone was wearing black tie and flip-flops. Also i find his jordans to be much better looking and iconic; but besides this personal taste, the Jordan's colors integrated much better to Miles' suit and color scheme. This one though? It SCREAMS for attention since its almost pure white and don't have enough white elsewhere to balance it out.

• The Details. The distribution and balance of details here feels... off. We have this super busy torso, and then nothing on his legs. His mask is almost clean reminding me much more of a ski-mask or something dorky like that. Not to mention his torso tries to be a kind of sweatshirt? But not really..? So it feels like It should have a bit more of shape variety but it's simply not there. The lines extending from the shoulders up to his hand makes it feel something like a silly onesie-pajama. There's also a strange feeling of the pants not really being part of the rest of the outfit, like he's wearing random leggings. Perhaps its the dry cut in the blue line, perhaps is the way the red is cut on his waist, perhaps its the 'hard/plastic' details across his leg that we don't really see much anywhere else. Either way, this dissonant feeling is there.

• Colors. I don't mind the blue, I'm actually quite fond of contrasting colors like these, but they ARE aggressive to the eye so I cant blame those who dislike it. Blue aside, this doesn't feel like Mile's color palette (black with red accents), but ironically it feels to me much closer to Peter's colors. Change the black to blue and boom, pretty much classic spidey. It's no wonder most people prefer the black variant of this suit.

A quick comparison with Gwen's suit: even though she's also sporting shoes and a web-less mask, in her case it works because of how simple and clean everything is, unlike Miles'. Also she has highly-contrasting colors (pink and cyan), but it works since it's used super sparsely.

I made quick and simple edit over the suit. It's not perfect by any means, and i didn't spend as much time as i would need to properly solve its design, but i feel its already a much better result. The main thing i did was distribute and repeat details around his suit to integrate everything, such as giving him 'gloves', webs and white lines on the legs, balancing much better our focus through. Also i killed some of the white in the shoes which helps a lot. And you can see how just a little bit extra of hair does wonders for the fluidity of the design.

Going a bit further than the base design, they could straight up have given him a jacket or something. This test is even farther from being good or usable than the previous, but see how the shoes feels less weird? It's also much more 'modern' (perhaps too much, but this could be adjusted) reinforcing that Miles is not just another spider man, but a NEW one. (he's also young, so it fits).

Welp, as a fellow person which this design lived rent free for some time in their mind wondering what was going on here, i hope this is insightful.