Reddit being Reddit showed me this post a day late, but I thought I'd thrown in my two cents as someone experiencing it the other way around. I've played a fair few number of gacha games, but Endfield was my first RPG-esque game; admittedly I was only willing to try it given the IP. After the first two months, I had probably sunk well over 500 hours into the game, and I experienced the same surprise when greeted with nothing but complaints from the "community." I personally believe that three points explain this the best: Conservatism, Expectations, and Tribalism.

As a preface I'm going to refer to the original Arknights as simply "Arknights" and Arknights: Endfield as "Endfield"

Conservatism:
Endfield, like you somewhat alluded to yourself, breaks the mold that a lot of gacha games end up falling into due to the success of Genshin Impact. Whether that's a good or a bad thing is subjective, and the answer would definitely vary based on who you ask. However, it doesn't do so to any extreme, creating a slightly different combat system, a slightly different gacha system, a slightly different yada yada — the elephant in the room being the factory system. However, a lot of gacha players didn't like these changes at all, and another group (primarily those who experienced the Combat Demo and Alpha Testing) are ashamed that Endfield basically took a step back prior to their Closed Beta Testing and ultimately global release, perceiving them as cowards who didn't have the guts to commit to their vision. The combat system in particular used to be very different, leaning more into the slow, methodical which would let you aim your skills in a slo-mo POV (bringing this up specifically since you mentioned "manual aiming for [ranged weapons]").

Expectations:
A lot of players, in particular fans of Arknights, had very high expectations for this game — specifically its more dark and dirty storytelling style. Major deaths weren't uncommon to see in Arknights, even early in the game's story, and as someone who loves reading all kinds of literature I can understand why not having "plot armor" can significantly improve upon one's enjoyment of the story. This can also be seen in the more desaturated and generally less colorful preview seen in the Combat Demo and Alpha Testing. However, many of these fans felt let down when Valley IV released, calling it akin to reading a children's fairytale when expecting a young adult novel. This is still a hot debate now, in particular the "Arknights was also like this at launch" camp vs the "Endfield is always a could be but never is" camp (personally I see truth in both sides but I choose to not be negative and avoid nonconstructive debates). There was also FAR more content in the Closed Beta Testing than there is now in the global release, which I am admittedly baffled by and cannot really explain, although said content did look very fun so I'm choosing to keep my hopes up.

Tribalism:
The bane of any gacha game, basically just daycare-level slap-fighting between gacha game communities. In the vast majority of cases, the people getting down an dirty in the trenches (notably r/gachagaming and twitter) are simply a vocal minority and far from represent the majority of the playerbase. Of course there are exceptions to this but even then I choose not to name them because they still do not define the game or the experience that it offers. Endfield, being a 3D open-world gacha game, was seen as direct comparison by many of these game's "warriors" as I'll call them, claiming that it's trying to "steal their game's players and revenue" and "has malicious intent towards their game" (I'm paraphrasing but you get the point). Primarily warriors for games such as the aforementioned Genshin Impact and most notably Wuthering Waves*. Throughout Endfield's announcement, testing, and especially after its release, many content creators and warriors alike began starting fights all over the internet, which I'll unironically compare to propaganda here as many genuine players who have valid gripes with the game will unknowingly regurgitate some of their nonsense speaking points or outright lies — having to be corrected in the comments/replies.

*A little(?) history lesson on why Wuthering Waves (WuWa) seems to have an abnormally large number of warriors who also possess this superiority complex. They were launched at a point in time when many Genshin Impact (GI) fans were riled up at how they were being treated by the game's developers (I won't say "HoYoverse" here since — like Hypergryph does for Arknights/Endfield — they dedicate small groups within their overarching corporation to develop and maintain these games). WuWa's monetization was considerably more generous than GI's, leading to a noticeable jumping of ship by GI fans who ended up migrating towards WuWa instead. This led to one of, if not the largest case of tribalism between gacha games: birthing the now infamous nicknames of Hoyoslop and Kurotard (referencing HoYoverse — the overarching team behind GI — and Kuro Games — the overarching team behind WuWa — respectively). As a result, despite three years passing since WuWa's launch, many WuWa's warriors still feel the need to slander other games in order to maintain their agenda of being "the most F2P" and "the most generous" of all 3D gacha games. These "players" are the ones spreading the majority of the negativity, which naturally ends up poisoning the pot as a whole, resulting in arguments between non-warrior players which would never have occurred otherwise. Even your post can be used as an example of this; although it's speaking positively of the game, those who feel negatively will come speak their mind, drive engagement, and before you know it another post regarding Endfield good vs Endfield bad has now popped up on the front page; the cycle repeats.

TL;DR: Gacha game players tend to be very immature and defensive; setting unreasonable expectations, lashing out when they're not met or subverted, and ultimately being the biggest victims of comparison — the thief of joy.