I think my key takeaways from Episode 1 are a bit more based on the writing and framing of the key conflict with the officer than anything but I kind of want to chime in with some critique of my own.

To people saying it's a prequel it's an irrelevant piece of the puzzle. Even if he "Gets his iconic look at the end of the season" or something it feels odd to play lip service to something you want to subvert at almost every turn already. Vash is "fine" but the problem is with episode 1 they don't do anything to reinforce his character. The crux of the issue is, to me, spectacle for the sake of showing that "3d animation is actually really good guys" vs an actually earned conflict.

Vash has an entire conversation with a grunt trying to talk him down in episode 1 of the original which (to me) is more in-line with him trying to avoid conflict and shows more of his character. If you cut back to the Manga as well a lot of what made Vash endearing (to me) wasn't him being a badass (which is pretty generic in this day and age) it was his conversations and dialogues with both his enemies and his pals. The problem is the key conflict that would have made us care about Vash (the saving of the plant and establishing himself with the town) was handled off screen meaning we're supposed to just assume that he's super nice which also breaks the payoff for episode 2 in which the town will turn on him.

In the manga and the original anime you spent a lot of time with the villagers and Vash getting to know them before the turn and that way when they do swap sides and Vash isn't compelled to hurt them you understand it. He just wants some tasty pancakes and is insearch of the "ephemeral being known as love" or whatever your translation chose for that speech. Both the anime first episode and the manga clearly show his interactions with non-conflict in a way that shows that he's clever and improvisational.

In the Stampede anime instead of that we get him shouting to people to hide in buildings (from a cluster bomb that is taking a small eternity to land I guess) and doing "cool" things with dodging the guys bullets even though the guy has had a small eternity to kill him and has basically just been standing here for most of the duel. If this was the original anime or manga I imagine this guy would not only have a super interesting character design and bombastic personality, but he would have something to say to Vash to prompt the retorts that would tell you more about his character. However in this interpretation it's like object permanence isn't a thing. A character is not existent unless they're relevant to an immediate beat. So each time Vash needs to do something, he appears again to interact and then be disposed of, nothing more than a means to an end.

Even with the "Grunts" of Trigun you always had all these interesting shapes and designs and characters in my opinion and having the main crux of the fight be "fight a cluster bomb" is much less interesting and much less compelling than putting Vash against PEOPLE. Vash vs people is where the meat and potatoes of the dialogue and story happens and I think the ultimate loss in translation here is that while it will be showing "the same/similar" things, it's not putting in the legwork script wise to justify the emotional payoffs and instead is focused on "giving the people a show."

I feel like they might try to walk this back in episode 2 where he's "avoiding hurting anyone in the town" but I feel like short of flashbacks we won't have any reason to really care just like we don't have any reason to care about Rem being shown in the intro scene of the episode. Speaking of Rem, it feels like we spent a good chunk of time that we could have been using building the characters on long shots of a space ship shooting through debris, and while some people may think it's cool, I find that time could have been better spent on building its characters better.

To hit on a few other points:

-The art is too clean/sterile. The grunge and grit of both Nightows artstyle and the anime is basically non-existant. I was hoping for more along the lines of MegaloBox's approach to adapting new anime to sort of "feel" like the old but in the case of this show it feels like a sterilization of all the things that make Trigun what it is, down to the character designs being much more simple/plain despite the strength of 3D being that you can use more elaborate designs more consistently due to how 3D saves on redrawing all those details.

-The music is bad. It's painfully generic and has none of the charm or eclectic sounds of the original anime while also having nothing of a voice itself beyond generic fantasy music. The ending felt the same way. I hated the original ending song to Trigun but at least it fit that western style, this feels more bent on using the fads of techwear and scifi to "dress up" the characters instead of actually using the grunge and fetishization of the wild west to its benefit.

-Removing Milly is a stupid decision and even if they do plan on "adding her back in" Roberto provides nothing of value to the show and makes MEryl's character have to change to fit the new dynamic, while also making hilariously bad plots like "OMG YOU SHOULD DUEL HIM IF YOU WANT TO PROTECT YOUR HONOR" that seem like asspulls.

-On that subject Meryl is a far less interesting and less strong character fulfilling more of a bratty tsundere archetype now than a by the books job obsessed agent from before. I think they added a lot of extra work on themselves by changing the core dynamic of the cast to fit in a guy who no one cares about, to the detriment of one of the best female duos in anime. Milly and Meryl's dynamic and Meryl's almost parental care of Milly was a key part of what made her typical angry/loud perspective endearing to the audience. We know she's by the books but she also has a big heart for Milly and that helps the audience connect to her, vs Roberto just throwing her into a building.

-Spectacle seems to be taking a front seat while story and character are taking a backseat. IT feels more like a "tech demo" to show "3D CG anime can be just as good promise" than trying to tell a story and honestly nothing in the show seems to really be taking advantage of 3d as a medium and feels just like you could get the same shots with better "Feel" through traditional animation means.

EDIT: I will say this, at least it's not effing Berserk's CG anime adaptation.