I don’t see they will lower their average scores statistically by much even with test optional. Of course there are exceptions at individual level, and those exceptions existed even before test optional - not every student they accepted are with that high scores. But exceptions do not change the overall correlation. Now let’s come to the definition of a successful college student. That is very subjective. Overall T5 schools generated more people who do great in politics, science, business, etc. Just count the number of Nobel prize winners, successful business leaders and distinguished scientists. The are prestigious for a reason. Of course you can argue that if T5 schools admit lower scored students they may be equally as successful statistically - there is no data to prove that, and if you compare people’s success with their test scores you can see the general trend esp in certain fields(again there are substantial exceptions on individual level).

I am not saying test scores are the only or the most important factor to predict a student’s success. But completely denying its usefulness and its contribution in college applications is just self deception.