nobody mentioned Long War so i'm mentioning Long War. ever think 30-40hrs wasn't enough for your XCom 2 campaign? ever thought it was kind of immersion breaking that these incredibly well equipped aliens couldn't swat down a ridiculously high-profile smash-n-grab resistance op foolishly headquartered in a single hovercarrier? Long War turns your chaotic gunfight missions into guerilla insertion and extraction missions, broadens your conflict from a months-long to a years-long endeavor, makes it MUCH harder to eject the aliens from earth while simultaneously making it a much slower process for the aliens to complete their doomsday plan, really makes you undertake missions on a global scale as opposed to the one- or two-region conflict that the base game tends to become, extends the available troop roster while forcing you to actually use more than an elite core of troops (because you have way more bases to cover), extends the max troops on a mission from 6 to 12 while allowing the aliens to field a LOT more forces (think 40+ enemies in some situations), making for some really HUGE fights near the endgame. really a spectacular rebuild mod, two thumbs up.

another really good mod for Stellaris is the Star Trek: New Horizons mod, a total conversion mod that was so good paradox got the envy and put out Star Trek: Infinite, which is just their own stab at a total conversion mod for Stellaris except they expect you pay 30 bucks for it, plus DLCs. New Horizons very worth it, give it a shot if you like trek and already have Stellaris