Dota isn't a game; it's a lifestyle. The high barrier to entry will drive away new players, but those who crack the shell and get hooked have a very strong chance of rarely playing anything else again. Its 100+ heroes all play differently, and coming close to truly understanding one could take hundreds of hours. Even then, there's always something new to learn. Every failed strategy, every death, every comeback is a chance to discover something new. Dota 2 is at its best when you're playing with a team of five friends. Gathering gold, killing enemies, taking objectives as a coordinated team, then making a final push to victory is an incredible high that you'll want to experience again and again.
