Yes Simone Inzaghi is better than Pirlo. How is that debatable? He has won Lazio 3 trophies, got them qualified and into the knockouts of CL, and has overall made them a consistently threatening team in Serie A.
Lazio has pathetic center backs, Patric and Luiz Felipe are midtable players. Only the signing of Acerbi has been good. Same story at wingback, old man Lulic was the only good player at wingback before Lazzarri arrived this season. Caicedo is poor, Correa is finally a good attacker besides Immobile. Their squad's shining area is the midfield, which Inzaghi has exploited perfectly. Luis Alberto was a reject, same with Leiva, and Sergej arrived as a kid.
Inzaghi deserves massive credit for Lazio's level. Most impressively he made a solid team with poor defenders that is also exciting to watch and effective in attack.