Sure... I think there is some confusion about this because it used not to be the case. Originally non-declinable quests never went away, so people would have to do things like rebuild the portal to the previous chapter to sell it for a quest, or be totally frozen out of the quest line. I guess there were enough complaints about this, plus the guest race requirements got increasingly elaborate, so that they changed and made them eventually convert to declinable.
The guest race quests are there primarily to guide you through the steps of the chapter, which is fine, but personally I've always slightly resented them because I prefer to plot my own strategy. I occasionally debate with some of my clanmates who facetiously maintain their compulsiveness obligates them to complete all the quests. That's perfectly fine of course, but it's nice to know you have the option to ignore them. They are a helpful extra but are not really fundamental to the game.