It won't ruin it but it will you make you less looked upon when it comes to applying.
It's not all about scores, because everyone is applying they look beyond the scores since everyone most likely has the same scores...so how are they going to choose??
That's when EC's come in such as volunteering or community service, any leadership roles in sports,clubs etc.
You need to get involved to enhance your application.
It won't RUIN but it can make your chances less likely to get into a specific school you want to get into.
Like i said everyone applying to a school most likely have the same scores as you, so they have to cut people...That where they look at your EC's.
They are extremely important when it comes to applying to grad school, after undergrad. Because grad school tends to be more competitive and obliviously it's more expensive.
Things that help:
Great EC's such as:
volunteer work
Community service
Clubs, honor society
Any leadership roles in clubs or honor society
Top percentage of class
any awards?
Great personal statement