“they are all top 20. Isn’t it good enough reason to dream about them?”
There are two things that bug me a bit about this question.
One thing is that rankings are arbitrary. Rankings change. Small schools (LACs) that provide a great undergraduate education are typically not included. Some schools are highly ranked in the overall rankings even though they are bad at some specific majors. The rankings mean very little.
The other problem is that high school students, and most adults, really do not understand what it means to attend a highly ranked university. Attending for example MIT or Caltech does not mean that wonderful professors provide you with thrilling lectures every day. It does not mean that you walk home with a smile from classes. It does not mean that people love you. It means a lot of hard work. It means spending Saturdays and Sundays doing homework. It means having very competitive students in your classes who are determined to do better than you so that they will get into the top graduate schools or medical schools. It does mean having some great professors (I remember five or six), but there are a few bad professors at these schools also (I remember two very well, but I don’t remember their names and would not give their names if I did remember). Once you graduate, it also means learning not to mention where you attended university because it sounds too much like bragging (which does not go over well).
MIT, Harvard, Stanford, and similar schools are great matches for some very strong students. They are not great matches for all strong students. They are probably not a match for any average or slightly-above-average student. There are many universities in the US and more elsewhere that provide a great education for a strong student.
There are students for which Columbia would be a great match and Dartmouth College would not. There are other students for which Dartmouth College would be a great match and Columbia would not. The same is true of MIT and Harvard.
I think that it is okay to dream about attending a highly ranked university. But you then need to wake up and find out what it really means to attend a highly ranked university, and to figure out what you want in a university.