So by now the flaws with both Kayle's and Morgana's reworks are growing fairly well known. Whether you like or hate the new designs (I hate Kayle's/like Morg's), it's hard to deny both feel unfinished. Many of Morgana's (most noticeably Blackthorn/Ghost Bride) skins are missing details and effects that they used to have. Kayle skins don't have new VFX despite being 975 skins that are supposed to get them. Aether Wing Kayle doesn't have the new/unique animations you'd expect from a legendary. Even if you like Kayle losing her helmet, the animation where she loses it and it just vanishes is janky as all hell. Etc. There's a myriad of actual problems with them all even if you do happen to be a fan of their new looks, and with each passing day it becomes increasingly unlikely that any of these issues will be fixed as time to make changes runs out. So knowing that most, if not all of these problems are going to go live and likely become permanent, I think it's pertinent to ask how it happened, and after thinking about it a bit, I feel the answer is clear.
Doing a simultaneous VGU for both champs was an incredibly terrible idea.
This isn't even just a screw up Riot made, as it's something the community wanted long before they were officially announced (though as the ones actually doing the work and making the calls, they do deserve the brunt of the blame for making the decision). In theory, the idea sounds super hype, as Kayle and Morgana are inextricably entwined in lore, and at the very least I don't think it'd be possible to rework either one without at least changing the other one's lore (and any interactions and VO likely would have at least needed to be planned together). At the end of the day though, actually doing both VGUs simultaneously was only ever going to cause problems, exacerbated by the decision to turn Kayle into some 4 form monstrosity.
Like, just look at the number of skins between the two of them. Ignoring their bases that's _seventeen_ skins. Probably closer to 26 once you take into account all the work that has to go into Kayle's multiple forms. Can you imagine if they had two new champions _and_ 17-26 new skins at the same time as them? Can you really imagine that kind of scenario and _not_ picture most of those skins being half-assed just to get them out the door? Hell, even half-assed, the amount of work that would be required to fix up all those skins is enormous, because they just can't possibly have enough artists to get the job done right while also needing to work on the rest of the new skins/champs/VGUs that came out recently/will be coming out in the following months. Hell, I'm pretty sure it would take at least another month if not more to fix all the problems at this point. So the end result is more work being put out for a lesser result.
Kayle and Morgana's reworks are looking to come out pretty sub-par, but it's not because Riot and all the people who put the work into them were lazy, it's because whoever made the final call to VGU them simultaneously made an extremely poor decision.