You're comparing a 975 to a 3250.
A 9 7 5 to a 3 2 5 0
#A 975 to a 3250
Let that sink in. Lux had more effort put in her skin over the length of at least half a year-- not to mention she essentially got 9 more skins than Nasus. You're comparing 1 measly 975 skin to 10 at least 1350, if not 1820, skins? Nobody complains about Nasus bc his skin is allowed. Why, you may ask? It's the Year of the fucking Dog. Unless you're insinuating that Lux is a bitch (her Q does make a convincing argument), she doesn't fit. Even with the Empress excuse. Karma could EASILY fit the bill more.
The issue doesn't lie in how many she has, but how short the duration between the skins she recieves them is. Same with Ahri and Ezreal and Yi and Jhin.
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As for your Jhin/Yi comment, did you forget that Esports/Worlds skins do not count towards the schedule? Just because SKT Jhin is a skin doesn't change the fact that it doesn't count towards his skin count/schedule. That's like saying Zed didn't have to wait three fucking years since 2012 to get PROJECT just because he had SKT. Sure, he got SKT, but only because Ahri didn't. It wasn't even a quality skin, just like the rest of the Worlds skins at the time, and it wasn't even fucking part of his schedule. Had Ahri gotten hers, Zed would have gone 3 fucking years without a skin. T h r e e fucking years. This would have been unless Riot decided to clump PROJECT: Yasuo with the PROJECT event releasing them all much earlier to accomodate, but even then, I doubt they had the PROJECT skinline fully figured out at the time with all the skin candidates and the story.
Nobody forgot that Yi got two skins in 2017-- in fact, the Boards were up in arms about it. Same with Jhin-- however, at least Jhin's skins had close to a year in between them. BMoon was released somewhere in Feb '17 with PROJECT around November or December? I don't recall. Regardless, that's a good 9-10 month gap, unlike Yi's 4/5 month gap.
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tl;dr
People are shitting all over Riot because Lux didn't need to get the skin, but got it regardless despite already getting an Ultimate not too long before (which was comprised of 10 skins in one). Esports skins don't count, so Jhin technically got one skin near the start of 2017 and near the end of '17, but everyone continued to shit on him along with Yi, who had a 4/5 month gap between his skins.