Accuracy is definitely important, and
everyone gets those 99.XX%'s with a half-assed combo (Most people like to put it tin their "HALL OF SHAME" or whatever name they prefer), but the combo is just a part of the game. If you really can't take it, then you should go make your own and see how many people complain about the rules of YOUR game. Everyone experiences combo breaks, you just have to deal with it somehow, whether that is through grinding or w/e. If you hate grinding (like me) just play through all your maps and hope you'll get a combo on one of them someday. If your accuracy really is 99.5% on something, it'll happen eventually. I usually play through (the whole song) maps once or twice and if it doesn't come it doesn't, w/e.
Maintaining combo, on the other hand, is a different skill. One can consider it even harder than getting high accuracy, because it requires flexibility. Any high-ranked player can press buttons with their left hand pretty much mechanically, the difficult part about osu is the right, or aiming hand (opposite for peppy and lefties
) (Yes I know streams take a ton of grinding) This is the more "random" factor, as fast jumps almost always have a luck factor. I'll exemplify my point with OWC 2013, in which I'm sure everyone sees how Rucker performs. (relatively) Low accuracy, with (almost always) FC, carrying the matches where SW drops combo. Sure SW is arguably the better player, with higher accuracy, but consistency is also important in the game. The ability to purposefully hit circles earlier/later in order to guarantee every hit in a beatmap is much more difficult than pressing your left hand with little inconsistency (game-relative).
Getting 100's and 50's accidentally is just natural error I'm not saying these are skillful. Purposefully doing so is what takes skill, and is highly rewarded in this game. One may have to sacrifice more notes (perhaps say 3x 100's) in order to guarantee a difficult part, while skipping the note completely could just easily guarantee 2x300 and 1x0. Examples are everywhere, take any fast screen-wide zigzag jump pattern. Getting 100's on all of them is much harder than skipping half of them, yet you get 30% for hitting and 50% for skipping.
In any case, I agree with GoldenWolf's post. Accuracy is important AFTER you learn to combo your stuff. Perhaps you could play some more Multiplayer?