Some characters are skill based some not (cough cough reaper)

At first, it isn't competitive at all. Once you play a few games and get into your skill level, you will be out into very competitive matches. Even more so if you're with a team. And once the ranked playlist releases later this month, it will be even more competitive. Skill varies depending on the character you use. Some take a lot of precision and timing, while others you can literally sit in a corner and get kills and assists. However skill almost always wins out in the end. You also have to know when to switch characters and who to switch to given the current situation, and team communication and/or synnergy is often key to winning.