Again, the fact that entry to the class system can be meritocratic is entirely disconnected from the fact of it operating as a class system.
When I worked at Big tech I remember recruiters (US-based) talking about hiring from approved schools, which were mostly Ivy League.
Additionally, when we were hiring a candidate in Europe, our director wanted to know what school she had gone to. Fortunately, she was an Oxbridge graduate so all was well.
Again, even if all Ivy League graduates were in the top 1% of objective merit, the use of this credential in hiring/firing/other decisions is what makes it a class system.
I have worked with many Ivy League graduates and they were all super smart and mostly effective, but that doesn't change my point.