Of course it's inconsiderate, the same way the whole premise of this topic is based on a very selfish sentiment.
If this is selfish then how selfish is leaving the game just becouse you don't like the map, you start to loose or play against specific strategy/faction? If you play automatch with random teammates, you agree to have random teammates, opponent and map. There are other modes for people who doesn't agree on this.
There is also a fair surrender option there to be used. This is a proper way of ending the game if you feel you can't make it, that's why it was implemented in first place. Leave option is just for people who really can't play to the end of match becouse of some urgency and don't want to leave the team with player afk. These people won't be hurt by 10 minute penalty.
Even the people who just have bad connections won't be hurt that much, as match waiting time for good players is just as long or, for really good ones, much longer than that. Only the ones who jump from game to game waiting for conjunction of planets in a match will get hit but they should as they are parasites of the playerbase.