I agree with OP.
Lots of the usual cliches are coming out about pushy middle class parents etc, but it is not that simple.
We live in an area where state education choices are grim. This means that many people, rich and poor, scrabble around trying to find somewhere where their children can be educated and feel safe. Being middle class does help. It means you have the resources to move house, to rent a flat somewhere else, perhaps have children "live" with grandparents somewhere more leafy. It also means you are more likely to be Christian and to take the State School route or to pay. Or you can tutor your kids to the nines.
Tough if you are a newly arrived asylum seeker or migrant who is already worried about raising teenagers on an inner city estate and does not know enough about the system to play it, yet desperate to use education as a route to a better future for your children.
Though mine tried for a couple of selective schools (including Tiffin) we did so without tutoring and, honestly, they got nowhere. They did get into good selective London day schools where they are thriving. I know one child who got in, via the wait list, without tutoring though with lots of home practice, and she is not only towards the top of the year group, but is also the only one of her friends who was not tutored. Some exceptionally bright children (major scholarships to top schools) do not get Tiffin.
Though fees are a real struggle, the combination of a long daily commute to a grammar and the two or three years of daily VR and non VR practice did not appeal. Education should be education, not exam-technique, childhood should be childhood, and out of school activities should be more than test papers.
Ironically if my children stay where they are within their year groups they can be predicted to do better than many at Tiffin. Some of this may be down to smaller classes, or more resources. However it suggests that if Tiffin is really selecting without bias and taking the brightest, they are not doing very much with them once they get in. (There are about 600 girls out there who did better than my daughter in the test and also did not get a place!) Or that places go to the most prepared not the brightest.
As well as possible language and class bias there may also be a cultural bias. The system may favour large extended families with the experience and ability to support preparation, above say the child of a single mum who is already working two jobs to keep heads above water.
I don't know if the solution is not to get rid of grammars, as they represent an opportunity to some who would not otherwise have it - and clearly people are desperate for that opportunity. The mad tutoring phenomenum is more a symptom of concerns about the alternatives.
The system is now so deranged that it almost represents child abuse. The OP is right to be angry. Children are spending two, three, or four years practising VR and non VR when they could be reading books, playing, taking part in sport, learning an instrument or a language. What happens when they get in? Or if they dont?