Now that's just silly. Mary added nothing unique to Jesus' birth or life. She was of David's line and a virgin. There were plenty of other woman who would have filled that position just fine.
That's like saying how can you cook pizza without a microwave. You use an oven or a toaster oven or even a stove top. The microwave adds no nutritional value to the pizza.
Other than Jesus, there is no person in the Bible could could not have been replaced.
You might as well ask how we would be saved without Pontius Pilate.
So your mother added nothing unique to your birth or life?
Looking at the beginning of Matthew, the lineage of Jesus went through Hezekiah, Mannaseh, Josiah, etc. If Hezekiah had not been granted the additional years, there would have been no Mannaseh. So I am sure God would have found some other way to fulfill His promise to us all through the prophets.
Ouch! I've never seen God's plan reduced to such relativism...
With that attitude, it's kinda surprising Jesus bothered "hanging around the lady" for 30+ years while only spending 3+ with His apostles..
and performed His first miracle of His ministry at her request..
and used one of His last Human breathes exclaiming, "Behold your mother"..
In fact, it seems clear she was very important to Him..