Would this hadith not contradict the concept that mujtahids will answer on our behalf on the day of judgement?


It wouldn’t. Everyone has to answer on day of judgment. As Allah says is Quran: كُلُّ نَفْسٍ بِمَا كَسَبَتْ رَهِينَةٌ

Every soul is held in pledge for what it earns. Chapter 74:v38