Match making games are designed to be competitive with people trying to compete. If you don't have the time or willingness to play against a random opponent who might have a slower deck then play custom games. You can justify it in your head all you want, but you're still in the error. If you believe someone has a build designed solely to win due to stalling the game and making you time out then report them for it. However, that's a super rare occurrence and you're really just reaching for things to justify your actions.