Idk maybe just play normally. Your opponent probably self-destruct playing a complicated opening like pirc.
Pirc Defense

As White 1) e4 d6 2) d4 Nf6 3) Nc3 g6 4) f4
"The strategic mistake" to avoid making and that "everyone makes" is [in my opinion] a 0-0-0 vs 0-0 because player with Black knows how to play while 0-0 vs 0-0 he doesn't really know and he undergoes a game where player with White has a space advantage.
If I'm playing black and white starts with the pirc defense, what would be the best way to respond to it?