Objective qualifications are not the primary filter. The biggest advantages are from a higher level of networking, your fellow students are generally from a higher income bracket, have better connections, etc. Similarly the best paying firms tend to focus on the more prestigious universities as well.
All of this leads to a situation where wealthy parents have the education and means to ensure that their children have the advantages to give them a better chance of going the more selective universities, adding another level of systemic injustice based on wealth.
All of this leads to a situation where wealthy parents have the education and means to ensure that their children have the advantages to give them a better chance of going the more selective universities, adding another level of systemic injustice based on wealth.