Klopp had won 2 league titles in Germany (and that's just with Dortmund; not even counting Mainz) in roughly the same span as Gallardo and fewer major trophies overall (3 vs 7 for Gallardo), but he was still considered a top manager. Nagelsmann hadn't won anything when he was appointed to manage Bayern, but he was still considered a top manager. Poch hadn't won anything with Spurs or Soton, but he was still considered a great manager (if anything, his stint with PSG, where he won trophies, may have tarnished his image a bit).
So I don't think you can judge a manager, especially one as young as Gallardo, simply on trophies.