By the first glance, Genshin looks like a bit-for-bit clone of BotW. While it did has some gameplay mechanics from BotW, Genshin, strictly speaking, is not a rip-off. From the perspective of gameplay mechanic, claiming Genshin ripped off BotW is pretty much saying Batman Arkham Asylum ripped of that 2002 Spiderman game.
The main problem in this whole Genshin farce is this "BotW look-a-like" appreance. Developers of Genshin definitely have the ability to change it, to make it look original, but they choose not to. These are the people who made Houkai Impact, and that game has elements from Devil May Cry, but still looks original enough. It is believed that this is basically negative publicity marketing, because apparently all publicity is good publicity. Even the name of the game, which literally means "re-enacting a classic", is hinting that they want anyone looking at this game to instantly think "Is this a BotW rip-off or something?"
When the PR shitstorm strikes just as planned, Genshin developers made absolutely no attempt to sterilize the tide. They did, however, release an announcement basically claiming that the negative previews of Genshin are the results of misunderstanding. They claim that they love BotW and they learnt a lot from various classics. They also subtlely hint that some Genshin haters really couldn't care less about the content, they hate because Genshin is not a foreign product like BotW. Needless to say, adding political element only makes shitstorm worse, and both sides now firmly believes what they are doing is for the best. It's basically "Chinese gaming industry can't be build on shameless rip-off products" vs "Chinese gaming industry needs a strong foundation by learning from something good", and whether you think Genshin is really a rip-off.
BotW fans tried to make Nintendo aware of this and sue Genshin for plagiarism, but didn't successfully pull it off. On the other hand, because Genshin is technically not a rip-off, backlash from Genshin fans are exceptionally strong. Sony approved Genshin and officially added it in PS4 store, and this is considered a victory by Genshin fans. A BotW fan smashed his PS4 in front of Genshin stage on China Joy to express his anger and disappointment of Sony's decision.
If you click in the source link, you'll see (provided that you can read Chinese) that most comments are insulting the artist for taking BotW side in this farce.
The gameplay is very different, which is what matters. You field 4 characters at once (8 in Spiral Abyss), and the core combat mechanics revolve around switching between them for elemental combos, which is pretty fun.
