Let me start with something my late father once told me:
"Wherever you are is the worst. Wherever you're going is the best. And wherever you left isn't as bad as you thought it was when you were there."
It tends to be true more often than not.
The OP mentioned a possible career in law enforcement -- FBI, police, etc. First, in order to be an FBI agent, you must be a college graduate. Many special agents also have law degrees. And most of their work is administrative. Most never, ever fire their guns other than to qualify on the range.
I've worked with police officers (an internship years ago). Most of what they do is write up reports. They testify in court about traffic offenses. They try to settle domestic disputes. More senior officers (i.e., detective) investigate crimes. Now THAT is paperwork. Again, most police officers never fire their weapons in anger. So, before you leap into another area, be sure to check it out.
Now, as to USNA and cynicism. In my day (and I assume it's still the case today), there is a lot of cynicism the last 3 yrs. IOW, it won't go away just b/c you sign the 2 for 7 papers. HOWEVER . . .
USNA is not the fleet. I can tell you that some of the most cynical people in my company are STILL IN THE NAVY or USMC -- 27 yrs later! And, conversely, some of the "true believers" were gone in 5 yrs. Now, I'm not saying that's universally true about cynics.
The point is that USNA is not representative of what you'll do in the fleet/USMC and, once you get there, you may find you love it.
Even if you hate it . . . it's ONLY 5 years. That may seem like forever as you sit here today (age 19/20). Trust me, it's no time at all. And what you learn and do in that 5 yrs, regardless of your service selection, will stand you in great stead for the rest of your life.
Finally, as a general rule (there are exceptions), those with college degrees from wherever end up in some sort of managerial/white collar position. Most of those positions require a fair bit of paperwork and administration. You can be the person being managed/led -- nothing wrong with that. But if you have the skills to be the leader, you will likely chafe as the one being managed/led. Not to mention that, again as a general rule, you will make less money.
There are very, very few jobs in life where it's 100% excitement and action all day long. Actually, I can't think of any.
Once you leave USNA, you can't go back. You've burned the bridge. Make sure that's what you want to do before you want to cross that bridge again.