IMHO, walking a Camino ending at Santiago and NOT visiting the Cathedral is like taking a long walk, without a clear purpose like just taking a long walk around the block. Visiting the Cathedral, paying respects to the relics of Saint James therein, or simply spending quiet time in contemplation at the immense effort that went into building this massive edifice nearly one thousand years ago, makes the long walk a pilgrimage.
The original and ongoing primary purpose of walking a Camino into Santiago is precisely that - to reverence the person / relics of Saint James, the Cathedral, both, or any other spiritual purpose. To avoid that discounts your effort, turning it into a long walk, lacking a defined purpose other than mere arrival.
Instead of something that might provide spiritual benefit, the exercise becomes merely a long hike from point A to point B. To me, at least, this is sad. There is much benefit to be had even just sitting in quiet contemplation in the Cathedral when no Mass is occurring.
I respect the right of any pilgrim to walk their own pilgrimage, with whatever justification they desire - and there are many. But, it seems to me that walking to Santiago so many times, and not at least paying due homage or appreciation to the proverbial center of the entire Camino universe is like drinking dehydrated water. The primary, critical, essence of the entire thing is missing.
But this is just my opinion. Everyone is free to disagree.
Tom