If you are relying on your auto attack to start your combo, your mysteries must be completely terrible along with ur init. Fire main has one of the best auto attacks in the game, being to hit multiple targets that don't have to be a specific position and have an auto attack that can completely control opponent.

You said nothing about his mystery and you are comparing them. Fire main's shield mystery basically allows his team to be unaffected by debuffs for one round, and it can ANY unit. Wind only can give 2 and it has to be female, while LM has to be sword and only gives 3, and these both last for only 2 rounds, and u can't time it. A han or masked man can easily remove one units buffs, along with the now arising shisui and itachi anbu meta. Fire main gives all regardless of what the units are and he can choose when to use it.

You underestimate the power of mirror genjutsu. If your opponent doesn't have a mirror, they will have an annoying time dealing with your team if their first debuff is a control debuff, such as shisui chaos.

At end game, basically all the mains are used for support. Fire main is one of the strongest support, immunity + shield, ignite multiple units, reflect debuff, and all his chase skills cause debuff which is another plus. His clone is probably the most underwhelming thing about him but an end of the round sleep/ignite is still amazing.