If Qg4 is really so bad, then why was it a favorite of Botvinnik in his playing days?
I will reveal you a deep secret.
It wasn't.
Factly, Botvinnik wasn't employing 1.e4 as white - he had played only the Black hand of this (as well as similar ones) position.
Please check your facts better next time.
If Qg4 is really so bad, then why was it a favorite of Botvinnik in his playing days? Once Black has commited the f8 Bishop, g7 is a hole. Qxg7 is still possible on move 6 even if Black plays Ne7 as Ng6 following allows White the ability to escape to h6. Also, Rg8 for Black is no solid answer as Qxh7 is playable too. Even declining to take at h7 is OK with Qh6 and now Black is stuck in the middle. The g pawn is hardly poisoned here. Where Black goes wrong in the OP is f6, though Ng7 to arrive here instead shows over 40% win as White compared to 31% in the database.
Here is the main line Winawer and it has a win percentage of almost 47% to White and 33% to Black the move order is: