Are there exceptions to "show not tell" in fiction writing?

I am writing realistic fiction for fun (not for class). As much as possible, I give details to let the reader know what is happening. Some people told me to use more “showing” though.

An example:
My writing (this is stream of conscious):
Bob walked into the halls of Springfield High School again. Everything seemed the same as it was when Bob left for summer vacation. The ripped up poster in the hall was still there. Bryan is flexing his muscles and bragging about how he would beat up all the nerds again. Yes, this would be a fun year.

What some other person might write:
Bob sauntered into the bustling halls of Springfield High School, wearing a nasty scowl the shape of an upside-down U on his freckled face. The half-torn Springfield Football poster with all the faces of grinning football players clad in crimson was still displaying slightly slanted to the right on the yellow-plastered cafeteria wall in all its glory…

My fiction tend to have more philosophical, almost modernist (think Great Gatsby but not as great) feel. While I like the second example, it seems too detailed to me. It is certainly not my style. Also, I think that 1) it is a drag to write as I am always trying to find ways to describe the mundane colorfully, 2) it slows down my otherwise fast-paced action-packed story, 3) notice that I didn’t even get to Bryan in the second example.

So, I am wondering if it is ok to forgo “show not tell” if it is not my style or it does not fit the pace of the story I am writing. Or should I adhere to “show not tell” no matter what?

P.S. Please also keep in mind that I am time crunched and I write fiction on occasion to keep my mind off things and to relax.