(I cannot fit everything I know of in here and it is already too much for many who do not like long comments. There are Youtube links that should briefly cover the history of KLab's fraud, as Touhou AR is simply a re-skin of their previous games. You can find the links near the bottom for your convenience. Otherwise, please proceed.)
It seems a lot of people in (mostly but not limited to) the Western side do not know this. You may have seen in the comments, a lot of Chinese reviews are unhappy and for good reason. Despite that, people still don't get it, whether due to langauge barrier or what not. I, as a Chinese, would like to fill in that gap and communicate to the English audience of the Touhou community or even if you don't know about Touhou at all.
I should note, all artworks and assets are indeed legitimate in Arcadia Record, to clear any confusion.
The company "KLab", which develops mobile games, has previously been involved (multiple times actually) in plagerism and stealing assets. They (along with another company called DOBALA) made a game called Flying Witch (飞天小魔女 - this is the bootleg) in 2018 using what appears to be the Touhou cast, but nothing other than the character art resemble Touhou - one obvious thing are the character names in that game, are not what they're actually supposed to be (it's actually quite funny). The company has also reusued many assets from that game now in Arcadia Record e.g. Boss sprites during the boss stages. It was obvious that the game wanted to attract non-Touhou fans, but of course Touhou fans would find out.
In 2021, KLab came out with another game called Danmaku Fantasy (弹幕幻想), a re-skin of Flying Witch. This time, it actually presented itself as a Touhou game. Oh, but there was a shady English translation that had the word "spin-off" in its description (The Japanese announcement used "derivative work" which was the correct term as the game is simply a fan game). Spin-off would mean that it is a legit sequel to Touhou and that ZUN (the one person creator of Touhou) would have approved and worked along it. This is not the case of course. If you want to read a longer case about the copyright-related issue, check this English source: https://mimidoshima.wordpress.com/2021/04/27/did-i-just-read-ip-laws-for-the-sake-of-touhou/.
There were a whole lot more on why ZUN allowed KLab to create a Touhou game, in some way of fraud. This is just a little part of it.
This company has a whole timeline of stealing assets, artwork and music fraud from other small creators. It stretches beyond just Touhou, but Touhou was an easy target for its vulnerability (Team Shanghai Alice is only ZUN) and the appeal for a certain audience. Their promotions for Flying Witch were blatant makeshifts of stolen works. And now once again KLab thought they could bleach wash their history and appear legitimate. Arcadia Record is simply a re-skin of Danmaku Fantasy/Flying Witch.
As I cannot fit everything in here, I have attached two videos below that have well-gathered information:
Touhou Arcadia Record's Dark History: https://www.youtube.com/watch?v=1K2iV89PruY
A Copyright Infringing Touhou Game (Danmaku Fantasy) (watch English subs within the vid): https://www.youtube.com/watch?v=pGOxUaZ3K_w
EDIT: Alright, so it turns out Arcadia Record was not going to be a clean game with KLab's involvement. KLab has continued to have suspicious activities, but this time being very careful behind the scenes (none of that easily recognisable plagerism). Take a look at this page if you'd like to: https://moriyashrine.org/forums/topic/970-do-touhou-and-gacha-work-together-2022-touhou-lostword-danmaku-kagura-soon-to-be-closed-arcadia-record/page/5/#comment-8854 (refer to the first comment about AR) -END OF EDIT-
I hope you can understand our concerns. It is for some of us fans, a duty to protect Touhou, a community that dates far far back. Mobile games like these are not what we want the community's reputation to be like. I suppose there's nothing we can do to stop KLab - since they can just gold-dig and leave due to pressure - but at least we are trying and more people will be aware.
If you still decide to play the game despite all this, I have no saying on that. Just keep in mind that KLab is untrustworthy and disrepectful to Touhou and other communities, solely using it as a popular title for crashgrab. True Touhou fans and the people that support the rights of small creators and that their works be respected, know to stay away from such a game.
As a last. If you still wish to play, then play as you will, but an advice DO NOT. put any money into it.