I strayed off course simply exploring, clearing tombs, caves, towers etc. without completing any quests, for quite some time. Now as I go back through to complete campaign quests they are listed as incomplete and I must go through all the motions all over again. Is there any way I can bypass re-doing everything in order to make campaign progress?
For the majority of quests in Skyrim, the quest item and/or quest enemies do not appear until the quest has been activated. This is especially true for miscellaneous quests, where the quest location could be one of a number of different places. I think the game tries its best to send you to new locations, but if you've already been to all the possible locations for that quest then it would have to repeat a location. So unfortunately if you've cleared out a dungeon and then later on received a quest in the same place, new items and enemies would have spawned there and you will have to go through it again.
I'm sure there are plenty of console commands which would allow you to skip over the quests if you're playing on the PC.