Dominions are a choice, not a requirement. I think we've sort of turned them into one because back in the day it was exciting to build your territory, the allure of the map game was motivation enough to try them out and, over the years, they stuck because they've consistently been the thread type that is "low-effort", easily done, and most importantly,
rewarded. There's little stopping big major factions from just not pursuing more dominions for a bit. They have the buffer, they have the planets, so why aren't there more faction threads and storylines?
I think there are two main reasons for that. One, as above, the map gain has been an easy incentive for factions to continually pump out dominions because they're easy threads, they show you have activity, and you get something tangible out of it on the map that you, as a faction, can come together to and point at to say 'Yeah, we did that'. Invasions offer the same to some degree, but they're not as easy (the risk vs reward is heavily skewed towards the latter).
From the counter-arguments I've read (a perceived
need to do dominions) it sounds to me like people are just not willing or able to put up the effort to think of bigger storylines for their factions that don't involve just doing more doms. I'm not trying to condemn factions for doing this, nor do I blame them, I've tried to think of major storylines too, it's a pain in the rear, but when you control upwards of 50 hexes? You have all the territory you'd ever need to worldbuild on, to develop storylines on, to
do things with. I think the fact that doms have been the only threads with tangible gain, along with years of habit built to just keep doing them over and over, has created a perceived need to do them.
I might be completely of my rocker here, I'm willing to admit, but my point is: I think we can reduce this need for doms by creating more incentives for alternative thread types to be pursued by factions, that offer some reward other than hexes for a faction. One idea was my mandate proposition earlier in the thread that allows faction threads to be submitted instead of dominions for SSDs, but this is just one suggestion that doesn't even scratch the surface of what we can do to incentivize factions to do threads other than doms. What if we had rewards tied to the factory or codex? A special unit or a major bit of tech that factions can grind towards over prolonged periods of time? Idk I'm just trying to provide some kindling for discussion on this.
Ultimately, as much as I would love for all factions to pursue non-dominion activity for the sake of story and story alone, I don't know if that's entirely feasible right now based on the state of the community and personal preferences. I'm all for this decay being implemented, limiting faction size is good and I think that doms do have a place on the site (the decay effectively requiring factions to continue doing them to maintain their clouds). They can be great when done right and factions that are all about them can continue doing doms for the sake of gaining territory infinitely this way. However, I'd like to see some of the perceived necessity to continually force them out be reduced too, and more choices and alternatives, I think, are always a step in the right direction.
/ramble
EDIT: ohjeez, I guess I kind of echo what
Damian Starchaser
said. Typed this up before I even saw your reply, apologies!