I think there is a difference between constructive criticism and personal preference and opinion about art pieces. The first contradiction is that i consider particles a little art form, while you would likely laugh at me and just say that it's nothing more than a thing that makes the economy go in the game. Another contradiction is that you think valve-made effects are how all effects should be, while me and many of my friends think that valve-made effects are low-quality underdetailed and janky particles that relied on barely modified high-quality textures, and that those unpolished effects were made by people who didn't know their own engine very well, or maybe couldn't or didn't want to spend too much effort on a simple gambling encouragement. You say this effect is too detailed, as if it's meant for a different game, i disagree, the sparks themselves only use valve assets and i think do fit the game. If we started arguing about it i doubt we'd come to a valid conclusion. This is why i was deleting your discussions and comments. It's one thing to say you don't like something - it's disappointing, but there's that, but when someone takes their own opinion as the objective truth without any proper experience with design or particles it's just annoying.

Thank you for clarification. I know you said that you didn't want to argue about this, but I want to give my OPINIONS on what you've stated:
1: Of course particle effects are an art form. People should have the creative liberty to make what comes to mind, to an extent.

2: With that being said, I believe Valve-made effects were made "low-quality" and underdetailed because that's what TF2 looks like. If you look at almost anything in the base game, you will see that they are neither highly-detailed, saturated, nor "high-quality". I'm willing to bargain the particles Valve made were made not because they wanted to be lazy, but because they wanted them to fit this pre-existing artstyle. Even the ones that are saturated and use neon colors (purple/green energy) have little extra detail beyond the plain energy effect, which lets them at least fit tonally. The things that do not fit this description at all I believe do not belong in the game.
After all, If they were truly "low-quality" effects, then why are so many of them beloved by so many people? Effects like Aces High, Burning Flames, Stormy Storm, and literally every Hween unusual at and before 2014 are beloved by so many people and remain at high prices relative to their supply. The one time I feel that an effect added to the game matched these effects in quality was Pumpkin Moon, and that effect became uber popular.

3: I'm a little confused about your reasoning for deleting my comments. Of course it's rude for me to flaunt my opinion as truth, and I admit I've done that before and I apologize, but to delete someone's comment because you think it's wrong isn't fair.
I believe there are also instances where I don't think it takes someone versed in item-creation to be able to see the faults in someone's creation. For instance, putting a train on Engineer's head is objectively stupid because it looks way out of place in TF2; letting Spy wear a saturated red/blue suit that completely deviates from TF2's color palette is wrong.

If you want to keep your word and not argue about this then that's ok. It's clear we're different people and I don't want you to feel like you're wasting your time.

1) Limiting art to what it is and isn't just doesn't work, I'm not trying to give off my opinion as a fact, this literally is a fact.
2) If low-quality effects were mimicking the tf2 artstyle of the time - then why are some of the sprites so high-resolution? I think dead presidents sprites look low-resolution, but the original model and animations aren't, and making a high-quality sprite to squash and crunch it down sounds even more unprofessional. Knifestorn uses the knife backback icon - this isn't artstyle, this is just laziness. The skull from misty skull is photorealistic, which doesn't fit the low-resolution artstyle, the confetti sprites are uncomfortably realistic, and the circling heart just looks scuffed. The legendary coconut and the unknown jalapeno also, supposedly, were intended to be used for unusual effects - even if not, they are real-life pictures with erased backgrounds, and they wanted to use them in game, getting far enough to actually put them in the materials folder. As for people's preference, it is hard to argue with that. Maybe the deal is that people who work on effects are used to looking at them up-close, therefore see rough edges on all effects a lot easier, and have different expectations of their own effects. I suppose people want an understandable concept that fits many loadouts and is noticeable from a decent distance, for them an effect with clouds, sparkles, pngs or energies is just that, and not a uniquely beautiful and polished thing. Its kind of like comparing The Conformist to Diehard - both are excellent movies, but i doubt you've even heard of the first one, let alone seen and enjoyed it.
As for the pumpkin moon, well... Everyone i've asked in the particle community told me that it's at least not good. That includes the creator. Yes, Cheesypuff.
3) Well, there were artstyle guidelines, and valve still added the item, because guidelines aren't rules. So who should choose what belongs in tf2 and what doesn't? The community? Yes, because it plays the game and buys the items, and no, because it doesn't own the game and doesn't make the items. The creators? Yes, because they make the items, and no, because they don't own the game, don't play it and don't buy items. Valve? Yes, because they own the game, and no, because they don't play it, don't make stuff for it and don't buy the stuff they've added. I think the artstyle has just evolved - it's different to what it was and wanting to bring it back is just ♥♥♥♥♥♥♥ stupid. IMO.

Of course everything is art and the definition of it shouldn't be limited as long as the creator put passion into their work. But the limiting factor for whether it's good art or bad art in this instance is whether it's good for TF2 or not. I don't want random ass objects on merc's head or fluorescent red pants or some ♥♥♥♥.
But I'm curious: what do you think TF2's artstyle has evolved into? What does it allow that past TF2 didn't? What should it have? What should it not?
In my perspective as a TF2 player, the artstyle shouldn't stray from what it was day 1 because the in-game world was built upon that artstyle, and trying to change it would affect gameplay in an adverse way, no matter how minutely, and things like a train on Engineer's head or giving Spy a bright red suit just looks strange in TF2's world where everything is muted and fits a palette.
As for the rest of what you said, I don't feel the need to argue anymore since it comes down to opinion. You're a content creator, I'm not; we clearly have different perspectives.
Oh yeah I forgot about Knifestorm and the skull effects, those are pretty ugly.
Edit 2: It seems that people upon the initial release of Pumpkin Moon seem to have loved it the most by far, evident by the most replayed part of the video being at Pumpkin Moon and the comments: https://www.youtube.com/watch?v=iIVpwJBR6TE

we need a mod for this NOW!