We just ended D1 as well. I have felt the same way many many times over the year, but I've come to the conclusion that there are just too many factors to blame to actually nail down an objective truth as to why dental school sucks. It just does.
But to make it suck less, we have to figure out what exactly we can control in this situation. Sometimes, finding close friends in your class to hang with isn't something we can control. I've personally found that to be the case, and instead focused more on my grades. I knew that even though I'd be miserable holed up studying all the time while my classmates are posting pictures on facebook of themselves getting drunk at the bar, I'd be even more miserable knowing that my grades are suffering and yet I'm here at the bar desperately trying to fit in like an idiot because having friends is supposed to be important.
Screw. That.
At the end of the day, YOU are the most important person to YOURSELF. Letting anyone else decide to interfere with that, either directly or sometimes even indirectly through your insecurities, would be an absolute disservice to... how much tuition money are you paying again?
It's 4 years of your life. Make the most of it. Please.