I tend to find the idea of Sunday obligation as a bit - difficult. As everyone here has said, not going to Church on Sunday often means that one is not doing all one can to become closer to God.
OTOH, how serious that is really depends. Not attending one week might be quite out of character and have more to do with circumstances.
Or, there might be legitimate things pulling one somewhere else. If you have only the Sunday to visit with your non-Catholic familily who you only see yearly, and you get to church regularly every week, and will go mid-week instead - well honestly, I am not sure that it might not be better to see the relatives, that failing to do that might be messing up a real obligation.
Now, that is arguable - but my point is that whether not attending one week is a real example of putting a barrier between oneself and God could depend on many things.
It seems to me this is the attitude Orthodoxy seems to take as well.