Is it possible for Fi dominants to be socially inept?

[Olimpia]

Social ineptitude is inversely proportional to extroversion. Introversion is just a nice way to say call somone socially inept.

You can't be serious.

[Skepsis]

You can't be serious.

It is not an absolute Law, but generally yes, the scientific(not pseudoscientific socionics) understanding of introversion is that of a person focused inward And behaves solitarily. Solitary individuals by definition aren't social, hence not socially skilled. However, ambiverts(most people) show a greater degree of skill than introverts. True introverts tend to be really quiet and a little weird according to many true extroverts.

Only in Jungian "psychology" can one be a true "introvert" and socially savy.