I understand your point about merit being correlated with income and class. It is obviously true that wealthy, upper-class high school seniors will have higher test scores, more impressive accomplishments, and (frankly) superior academic abilities when compared with their lower-class counterparts. But you must know that this is attributable to differences in upbringing and opportunities, with varying levels of immediate relevancy (e.g. SAT tutoring, better teachers, parents who introduce intellectual discourse into the home). This means that any supposedly "pure" meritocracy, which does not account for those differences of opportunity, is going to be heavily biased towards those who were born into privilege. This creates a self-perpetuating cycle of class immobility that, I think, most people find undesirable. If you don't agree with the idea that two children with equal natural talents should, in a perfect world, have equal opportunities to pursue those talents, then I'd love to hear your version of meritocracy.
When you say "holistic" admissions, I'm not sure whether you mean holistic in the sense that colleges use it (i.e. taking evidence of talent outside of grades and test scores into account) or as a reference to programs which take race or class into account. Either way, you present standardized tests as the more meritocratic approach, which is silly. A perfect SAT score means a student is great at basic math, reading, and writing in an extremely specific context. That can be an extremely useful foundation, but do you honestly think that indicates this student is the "best?" That someone with lower scores who has published a bestselling book or won an international science prize or started a great humanitarian effort is on a lower tier in the meritocracy? Of course, all of these things are biased even more heavily towards rich students, but that's why class and background must also be taken into account.
I suspect I may have misunderstood parts of what you were saying, so please do clarify (if you can make it through my little word dump :P).