Talking about pick banning in ranked

I need help for pick baning in ranked
I always like to pick the brawlers that like on the specific modes and it may become a bad outcome. For example : i always use Nani in bounty, rico in maps with a lot of walls and i would never pick others.
Other than that the reason that is limiting my picking are also hypercharges and levels ( i am left with 17 brawlers to upgrade from level 10 to 11)
When i send my matches, people would say you need to learn how to ban pick , or else choosing random brawler will just lose the match