To answer your question: No. The main quest is not worth doing, to sum it up:
1st part, 'Neretze's Folly', I find this part cool for the background of the collapse of the empire but it could've been tied much more seamlessly to Arzagos desire to destroy the empire by having a sidequest or storyline that highlights the excesses and abuses of power in the empire. For any1 not interested in storytelling the first part is simply an annoyance.
2nd part, Assemble the banner - simplistic to the point of being an insult to any1 with half a storytelling hearth. Basically it's a second part tutorial on raiding the hide-outs. It's not just boring, it's a bit condescending to think that players haven't learned it by the first lesson and besides the hide outs isn't exactly rocketscience since everyone atleast understand the objective. A greater focus on logistics, horses to men ratio, bows/crosbows to swords etc. would've been more welcome imo.
3rd part, Destroy/Unify the empire: I simply can't see anything gained by the conspiracy plots. They're imo the worst thought out and implemented "feature" I've seen in a long, long time. My problem with this part of the quest line is basically the same as with the smithing mechanics, in smithing they went with the laziest option imaginable - RNG, and at the same time borked the economy to smithereens by somehow allowing insane sale prices for javelins. In this quest they basically introduced a grind element as a storytelling element. It would've been more interesting if they had added diplomacy, council, rights/obligations layers as those we see in Crusader Kings fx. and then made the quest revolve around first securing support for your house within a region (fx. all Vlandian villages/cities should have x amount of relations to the players clan, while having quests, trade, warbands etc. increase those relations including marrying followers to notables). Anything really other than what we got.
The final part is prob what I don't really see atm - what happens when you've finished the main storyline? - this could be solved by having the main storyline act as a tutorial to an indepth diplomacy, clan lineage, village/town, warstrategy tutorial and by finishing your clan is considered "homo novus" or a clan of "new men" at the top of societys hiearchy with the distinction of having proven yourself worthy to be considered peers of the realm, but the stigma of being upstarts.