I think this is such a departure from D&D as it is today however, that it largely is academic. Tasha's Custom Lineage with an expanded selection of feats, is likely as close as we are going to get and it still be "D&D".
In practice the D&D updates seem little or no change.
There are no longer "Evil races". But there are still normal D&D Evil encounters.
Look at the MMM (Mordenkeinen Presents Monsters of the Multiverse).
Yuan-Ti are a "Monstrosity" with a number of Evil organizations that serve as old school D&D villains.
(The Grummsh cult among Orcs functions similarly.)
At the same time, Yuan-Ti are also a playable Character Option, that the DM can choose to include in the Setting.
Moreover, the Skulk is illustrative. They are "soulless shells of travelers who became lost in the Shadowfell". Essentially, the Shadow plane has magically oblivionated these individuals. The process makes their alignment Chaotic Neutral, "typically". I suppose there are still individual Skulks who have flickers of memory of their life and their alignment values.
If the Skulks lack souls, I might classify them as Undead. MMM classifies them as Monstrosity. But in either case, they seem a good example of the need for a "Shadow" planar type that is nonidentical with the "Undead" type.
In any case, when players adventure and encounter a Yuan-Ti or Skulk, the encounter feels pretty much same as it ever was.
Racist ways of generalizing seem an unnecessary part of the D&D traditions.
Finally, the rule of thumb is: if the creature has a culture and it can learn, then it has free will and any alignment.
If the creature lacks the ability to learn, then it is no longer humanlike.
The Yuan-Ti definitely has cultures, and players who want to play one. So caution is especially necessary when describing them.
The Skulk loses the ability to have culture or learn new things, and is no longer humanlike. Albeit there can be atypical individual Skulks who still cling to their humanity.