Here is a shiur against the learning of Kabbala [or "Pnimiyus Hatorah"] for the masses.
The Lubavitcher Rebbe was a very strong proponent of teaching Kabala to everyone. What is Tanya, Likkutei Torah and Torah Ohr [all by the Alter Rebbe] if not pure Kabala and those sefarim are basic staples of every Lubavitchers diet.
Rav Moshe Schapiro ztz"l devoted a large percentage of his energies to spreading Pnimiyus Hatorah.
And there are many other examples.
Here are some passages from the Rav ztz"l [and see the Gra on Mishlei 7/12].
OF COURSE a person must also spend tremendous energies on the revealed Torah....