Helldivers 2

Say you have not played HD1 without saying you have not played HD1. The game was barely 0.06% as big as HD2 is in terms of playerbase if I'm not mistaken, and it had some very good long term support.

We will get pushed back to super earth and have to fight desperate defenses on more urbanized planets at some point. We can literally get pushed all the way back to super earth itself and have to defend it (probably with special missions and unique maps) or lose the galactic war. Also when we push an enemy faction back to their capital systems there will be boss fights to take these planets. Actually I'm pretty sure they expect to introduce us to the terminids' boss in a few weeks since they put a ton of major orders against them lately, and we are now very close to their home planets. Vehicles were also pretty diverse and I can only imagine what they have in store for us right now in that department. Also an entire enemy faction is obviously missing and there's room for a fourth one on the galactic map (HD1 only had 3)

But also, as other people have already pointed out, ultimately it's a kind of horde coop game. If you don't enjoy running the same missions with slight variations over and over in games like left 4 dead, vermintide, deep rock galactic, cod zombies etc, yeah, you're probably not gonna enjoy HD2 much more