Colleges want to know why you want to attend their schools – can you write the same thing on multiple essays? https://www.collegeconfidential.com/articles/can-i-recycle-my-why-this-school-essay/
The answer is mostly no, but a bit of yes. My daughter was able to recycle many of her essays, but had to modify each so they all read like they had been custom-written for each school (I reviewed them afterwards, and none looked like they had been recycled/rewriitten). It was less work than starting afresh for each school, but if she had used the exact same essay, it would have been readily apparent that she had used the same essay for multiple schools.
The answer is - kinda/sorta.
What worked well for my D was that she had a template of sorts that she customized for each school. She would generally find some architectural and/or artistic element on each campus that spoke to her (she’s an art history major) and would then weave her educational aspirations into an art historical interpretation of that particular artistic or architectural element.
The Ask the Dean answer is good.
If your Why Us answer is so generic thaat you can use it again, you may be in trouble. And, “You’re my first choice” is too easy. Talk is cheap. If you’re truly interested, show it with a full, appropriate answer. That’s not, “You’re a top college and I want a top college.”