Word for someone seeming deep and intelligent, but not really being that

Solution 1:

It's not common, but sciolist seems to have the required definition.

One who exhibits only superficial knowledge; a self-proclaimed expert with little real understanding.

I prefer this to sophist, which I think has a suggestion of deceit rather than just ignorance or error.

Solution 2:

The word sophistication is from the Greek word sophis, which implies false or pompous wisdom. Appearing to be wise. Which is different from the Greek words sophee, sophia which mean wise, wisdom.

Therefore we have in English the words sophist, sophistry and sophism.

We also have the words

Smarty pants
Smart Aleck (more prevalent in Brit English)

smar·ty-pants, smart′ al`eck

n. Informal. an obnoxiously conceited and impertinent person.
[1860–65, Amer.; generic use of Aleck, nickname for Alexander]
smart′-aleck•y, smart′-aleck, adj.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.

sophistry

n, pl -ries

(Philosophy) a. a method of argument that is seemingly plausible though actually invalid and misleading b. the art of using such arguments
subtle but unsound or fallacious reasoning
an instance of this; sophism

sophism

(Philosophy) an instance of sophistry. Compare paralogism

[from Latin sophisma, from Greek: ingenious trick, from sophizesthai to use clever deceit, from sophos wise, clever]

Collins English Dictionary – Complete and Unabridged © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003

soph·ist

a. One skilled in elaborate and devious argumentation. b. A scholar or thinker.
Sophist Any of a group of professional fifth-century b.c. Greek philosophers and teachers who speculated on theology, metaphysics, and the sciences, and who were later characterized by Plato as superficial manipulators of rhetoric and dialectic.

[Middle English sophiste, from Latin sophista, from Greek sophists, from sophizesthai, to become wise, from sophos, clever.]

Solution 3:

I'd call someone like that an intellectual fraud, poseur, pseud, phoney intellectual or — notwithstanding your reservations, which I think are feeble — pseudointellectual.

Solution 4:

Sophomoric suggests both limited experience and pretensions of knowledge:

suggestive of or resembling the traditional sophomore; intellectually pretentious, overconfident, conceited, etc., but immature

Wiseacre may fit, but is not widely used:

A person with an affectation of wisdom or knowledge, regarded with scorn or irritation by others; a know-it-all.

Solution 5:

While it is not limited to intellectual chicanery, charlatan means

one making usually showy pretenses to knowledge or ability : fraud, faker

Merriam-Webster

Or perhaps know-it-all

one who claims to know everything; also: one who disdains advice