Ok, now that I've had my fill of popcorn I can be a little serious here.
OP, it's a crap shoot that you got kicked right at the last boss because it does make the run useless to you. However, you're also blessed with the privilege of being a tank and thus you'll get near-instant queue times so it probably didn't set you back too far. Were they in the wrong for kicking you right before the last boss? I think so. Obviously they "dealt" with you through the whole dungeon up to that point and had only a couple of minutes left to either beat the final boss or wipe (and then vote kick you) so kicking you there seems petty, to me. As to the comment by the person who vote kicked you about trying to add you as a friend, I frankly would have blacklisted them as well. I've no desires to be friends with someone who does something like that.
However, as you're no doubt aware by now, it sounds like you weren't utilizing your toolkit to the best of your ability and honestly, that stuff can happen as a newbie. I've only been playing since July 2017 and I am by no means an expert at anything. I remember being around level 50 and still having no idea what I was really doing or what my rotation was supposed to be and unfortunately I never had anyone in dungeons who attempted to help me, though I would have welcomed it.
Sometimes there's something to be said about being humble and recognizing that as a new player or even a new-to-class player, you're not going to know the ins and outs and will have to defer to someone else. If more than one person in an instance is telling you the same thing, logically they might be correct and at the very least, it doesn't hurt to try to follow their advice and see how it goes. If you succeed, then you've learned something. If you fail, the egg isn't on your face. Accept that you probably don't know everything and be open to polite criticism. You'll grow that much faster as a player.
Take the advice offered here on the forums to heart. The majority of people in this community are merely trying to help and teach. The ball is in your court how you respond to that. I find that you will have much more success in a class if you take full stock of the advice given and try out the techniques/tips on a practice dummy.