One of the biggest sticking points in Destiny 2's first expansion Curse of Osiris was that many of the expansion's strikes were recycled from the game's campaign missions. Unfortunately, it appears that more reused Destiny 2 assets were used with Warmind, and fans aren't happy with Bungie in the least.
According to reports by various forum goers of the ResetEra forums, the two "new" Strikes that we got in Warmind are literally just the last two levels of the expansion's story with little to no differences at all.
It's likely that Bungie is reusing Destiny 2 campaign assets in order to cut down on work, but when it comes to player satisfaction it's definitely having the opposite effect. Especially in regards to the original Destiny, where the game got better with every expansion before finally apparently hitting its stride with The Taken King.
The newest Destiny 2 expansion, Warmind, takes players to the poles of Mars in order to protect the Warmind Rasputin from an army of Hive frozen beneath the ice. Players will be helped in this by the Hunter Ana Bray, who is investigating her pre-Guardian past.
Bungie putting reused Destiny 2 assets in their expansions is unfortunately nothing new. They did the same thing with the Curse of Osiris expansion, and what makes it worse is that the only Strike that's even remotely original is locked to the Playstation 4 version of the game as a timed exclusive, meaning that other players likely won't see it for months or even a year.
Perhaps even more annoying, in Curse of Osiris Bungie at least put in different dialogue and mildly different paths through the Strikes and campaign missions, giving it a bit of variety despite both taking place with the same assets. Apparently in Warmind Bungie even used the final boss of the expansion as the boss of a Strike.
If you still want to buy Warmind for its $20 price tag in order to continue the game's story you're welcome to it, but unless you're on the Playstation 4 version of the game you might want to avoid any of the expansion's new strikes. Hopefully in the next expansion Bungie will finally get its act together and stop using reused Destiny 2 assets.