RE: Multiplayer and longevity - there's a reason developers focus on multiplayer. Once you finish the campaign, there isn't much to do in RTSes, only the PvP people are keeping the game alive.
A game doesn't need to be "alive" to make the developer money.
In fact, a game being purchase only with no MTX actually costs the developer more the more people keep playing it in multiplayer, with all the necessary infrastructure and development necessary for it.
It's a myth that people keeping playing a game
specifically in multiplayer are necessary for longevity.
If that was the case, other single player games that have obvious longevity would not exist - they clearly do, and they are cheaper for the developer than trying to achieve the same for multiplayer.
In the end, if you want longevity, you need a community to form around a game, no matter the genre and no matter if SP or MP.
RTSs regularly fail to do that for various reasons.
The reason developers often try to focus on multiplayer for community building is because it seems to be easy to them.
But it's not, the MP RTS crowd is elusive and picky as hell, even moreso than the much larger SP crowd.
It's a stupid move by corporate suits rather than someone who understands the audience.
Look at SF3, it has an extensive campaign, 2 expansion campaigns, journey mode and skirmishes, yet the game is a graveyard.
And people came back to buy the first standalone expansion as well as the second.
In numbers that are about as expected when it comes to expansions (looking at the review numbers compared to main game, at least), or maybe even better (considering people tend to leave way fewer reviews for expansions than for the main game).
It made its money back, unless they were for some reason expecting a breakout success without any real marketing, in which case the publisher just messed up.
It is dead now, yeah, but I don't think it was a failure.
A community cannot form around a game that was pretty much just thrown onto the market with little to no fanfare or community building neither before nor after release.
And their absurd attempt at going for the MP crowd with that weird "free" edition speaks for itself... nobody cared, because nobody was interested in MP in that game to begin with.
You "only" have to make the single player experience engaging and varied enough for people to come back.
As well as provide some kind of continuous support to keep things at least a bit "fresh". Or proper mod support.
A story-focused campaign won't do that, no matter how good it is.
The journey mode is just a bunch of skirmish maps with absolute minimal glue connecting it.
Compare it, for example, with DoW:Soulstorm which still has people playing the campaign, or modded campaigns. It isn't great, but "good enough" and more importantly, the game has so many factions that that alone provides replayability in such a sandbox-y campaign.
Or WC3 with its custom maps birthing entire genres (and often perfectly playable alone even though you often needed to be online).
Or the Warhammer TW games. Sure, CA messes stuff up relentlessly, but the base game and mod support provides years of longevity even with their bullshitting around.