The official pokemon games do a horrible job at preparing a trainer for competitive pokemon. All of the games encourage you to just run a team of 6 sweepers to wipe the floor with enemies doing Super Effective damage. It always works and you can beat the games quickly just doing that.

The only pokemon game that sets you up to learn about tank/utility pokemon is Pokemon Colosseum with Umbreon and Espeon's team dynamic. Espeon is there to be a sweeper and Umbreon is there to soak up damage and spread status and/or heal with Wish. Pokemon Colosseum has done more towards opening my mind to competitive pokemon concepts than all of the mainline Pokemon games combined.

I think the pokemon games oughta do a better job at teaching players about the different kinds of roles a pokemon can play in a match and force players to use them to win. There has gotta be a way to punish a player for just picking a team of sweepers.