What even is this game about???

I think people like it for various reasons but for some its just a relaxing way to pass the time, and for others its really stressful and competitive.
It's basically a game of tug of war between the two sides, but it has RPG elements that reset at the end of each match, so its a mix of big picture strategy and smaller levels of action to get to the end. Everybody sucks at it when they first start, for at least the first month, but you could always try it out and get through the tutorial and the matches against the AI if you want an idea of how the game works. Honestly its hard to explain or enjoy until you play against other people and start to learn whats going on.

You have to destroy the enemy base faster than he will destroy yours.

Its about fighting with other team. You can pick your hero.

Like the other guy mentioned it's stressful and competitive. Just like most other competitive games it's got both low and high ranks. Everyone wants to get to the high ranks before quitting (or going pro haha).
I've been playing the game since season 2 and I'm only in diamond. By far my favorite game due to the challenge and individual skill that is required. ( even though it's become more of a team game over the years, sadly )

About dominating and rise up on the rift with teammates

in short i would say it is a game where you win by using your enemies disadvantages and turning them into your advantages. Some people might argue it's about mechanical skill but at thte end of the day it's usually the smarter/better teamworking team that takes home the victory.

Just don't play fortnite and all game are good (gmod are good)