Applying to a raid isn't applying to enter an instance. Applying to a raid is applying to a team. Joining a steady raid group isn't signing your soul away to WoW, it isn't declaring your dedication to the game itself. Your application is to the people, a statement that you want to join a team. This doesn't just apply to WoW, either. It doesn't just apply to this game, it isn't a flaw in World of Warcraft.
Real life has these same situations. Can you go bowling by yourself? Certainly. However, if you want to bowl competitively in the team brackets, there's a level of dedication required. It is a game, but you're also asking to be a member of a team. That team can be your friends playing for giggles, sure. If you want a very active team capable of competing, you'll need to prove your worth. You need to show up at the appropriate times on a regular basis or you are not a desirable team member. Bowling is a social activity. So is an MMO. If dedication to your teammates is a flaw in WoW, then life itself is flawed. If being able to commit to others is an unimaginable task, well... there are other problems at work.
High-end raiding in World of Warcraft is much the same. Your dedication is not to WoW. Your dedication is to the other players, to your teammates. If this makes you uncomfortable, find content that won't require this of you. Find people who will not mind a lack of dedication on that level. They exist. There's no reason to be smarmy about people asking you to be dedicated. You're not playing for you, you're playing for your team.