I've met plenty of engineers (anecdotally, not a majority, but enough that it's a clear pattern, and strongly correlated with how junior they are) who lump soft skills into a single category represented by broad labels like "charisma" or "schmoozing" or "eloquence". But it's really a very big category of practicable skills.
Things like navigating an org, knowing how to make asks that have a high % of being accepted, writing things for a specific audience and keeping conversations on track are all very important "soft skills" that are completely hidden by the "soft skills" label.
Trying to munge these all together under one label seems counterfactual. Certainly, they're very different sets of skills: the former are social, the latter overtly political.
You are also right that a lot of it can only be approximately taught, because the process of internalizing the skills has a lot to do with figuring out how to work with your own personality.
The more trustworthy and time-efficient way is from coworkers/ mentors/ friends.