Dyson Sphere is one of a kind, but Genshin copied most of its mechanics from Breath of the Wild, and as you said it yourself, Portia is basically 3D Stardew Valley, while Black Myth: Wukong is similar to Lies of P (from South Korea) in being an incremental improvement on existing "Souls like" action games (though it is probably closest to God of War in inspiration).
Game design innovation does not come from coding skills, but from devoting time & effort to design iteration. Game design, in my observation, is still a young industry in China, and Chinese game designers tend to be more derivative because historically, derivative games were highly successful (see two of the most successful games in China - Honor of Kings, basically a League of Legends clone on mobile; and Player Unknown Battle Grounds Mobile, whose name speaks for itself).
For China's game industry to get out of this pattern, Chinese gamers need to develop more sophisticated demands than AAA production quality and marketing. And we know it can be done because Japan is actually the source of a lot of gameplay innovation in recent decades. So it should be possible for China to do more in this space. Think one reason why it doesn't happen more is also government regulations - the limited number of approvals per year kind of limits more experimental games.
By your description, we could say that: Cyberpunk is just a sci fi themed Elder Scrolls, God of war 2018/Ragnarok is just Dark Souls with a bit more story, Lies of P is just Dark Souls with a Sekiro parry mechanic, FPSes and Assassins Creeds are all just the same game copy and pasted forever with different skins, turn based RPGs are just ye olde final fantasy titles with flashier graphics.
So I think it is strange to say that "Most Chinese games today are imitative on the gameplay side and the depth of gameplay is often lacking" -- one can remove the word "Chinese" in that sentence and broaden it to mean all recent games in general, in the world.
Successfully iterating and innovating on game mechanics and traits if anything shows why two examples you criticized (Genshin and Black Myth) are successful.
Genshin's real time quick swap elemental combat and continuously growing map and character roster is a fresh touch on an open world exploration loop that succeeds despite being in a GaaS gacha business model.
Black Myth is able to bring a bunch of action RPG staples in a melee combat system that is simple and complex and using a weapon type that is rarely featured in most games, combining it with real time use of spells and unique bosses with cohesive art direction and lore.
All of which isn't to say that the Chinese game development industry has matched, as a whole, that of Japan or the US/west -- however I do think that there isn't anything particularly "innovative" out of games that companies in Japan or the US/west (or anyone else) has pushed out in the last decade or so, in terms of game mechanics or design. Instead, they are understandably iterative, and that's okay because you don't need to be "innovative" in mechanics or designs to be a good and satisfying game.
Genshin pulled basically everything from Nier Automata.
Apart from having a weapon that floats behind their character model, I don't think there's any particular resemblance to Nier Automata.
There are certain open world/exploration traits that it shares with Breath of the Wild, and one or two minor aesthetic similarities to Nier Automata (fan service gooner bait character models being the other possible similarity), but everything else about it is fairly unique (in so much as an open world RPG can be). The real time quick swap and elemental reaction system is something that Genshin executes well that I haven't seen other games do as satisfyingly.