I went through a PhD at a non-top-tier school (borderline between second-tier and third-tier). I definitely dealt with politics extensively. A huge amount of people-pleasing, both with your advisor and with others in your chosen research area and the broader field it sits in. A fair bit of funding-related politics. And a fair bit of actual politics politics, if you want to fit in.

There's a lot of in-group / out-group politics in academia; don't make life more difficult for yourself when you know a straightforward way to survive. Learn to deeply bury any opinions you might have that don't completely align with those of people who control your fate, especially in areas fundamental to their in-group identity, and if that fails, lie convincingly. (Remember that dodging a question where enthusiastic agreement was expected is a form of answer, and not the one you want to give.) You might get lucky and work with people accepting of differences of opinion, but I wouldn't recommend risking it when years of your life are on the line.

I don't regret the experience, and quite frankly I learned a few other survival skills in the process that simply hadn't come up as an undergrad, but don't go into it thinking it's a purely technical experience, or that you won't have to deal with a pile of utterly ridiculous BS and unpleasantness.

Having spent time at schools of various "ranks" (whatever that means), "politics" (whatever that means ... that's super vague) is everywhere. It's what you make of it. Whenever you have people, money, and status mixing, there is politics. That's not exclusive to academia. Every company I've worked at also had those dynamics. Want to eliminate politics? Be independently wealthy and work alone :) Otherwise everyone needs to learn to work with and transcend the system in their own unique way.

That's good to hear. I have the hankering to return to school at some point, and I really just want to learn and contribute.