You can still play your way, even though I think it's boring. All you have to understand is that some people don't play that way. You don't have to understand why someone would want to do anything other than put one foot in front of the other and dutifully go through the main quest every playthrough.

That's the way they design their games, so they ought to give us the option to assassinate whom we want, if that's the kind of character we want to play. My experience in this game is not tied to the main quest unless I say it is. People who for some reason go into their menu, toggle killing 'essentials' on, ignore the 'essential' symbol on an NPC and then ignore a warning message afterwards should just be allowed to ignore the main quest (as OVER 9000 people do anyway), including the 'necessity' of the NPCs that were supposed to be important to it. They put a main quest (which consists of a generic, average story) in front of you and then kindly GTFO of your way so you can either do it or choose to go off and be an assassin, thief, wanderer, etc. Have you ever played a Bethesda game before? This isn't an on-rails game, the whole point is YOUR story, not theirs.

No essential npcs skyrim