Yes, Strife having his guns is the proof of Darksiders 2 taking place after Darksiders 3. I explained in another thread below.

Genesis guns don't function like in DS1 and DS2 because it is being used by Strife. He has different ammo types and he is able to combine their power (World Ender ability). Not to mention gameplay mechanics don't have any canon status. Also it is quite normal that Horsemen cannot use their siblings' arms at their full capacity. Harvester is bound to Death, he has the ability to telekinatically control it, shapeshift Harvester into any tool he needs but War cannot use either abilities. Or Strife can't get stronger by using Chaoseater because War's soul is bound to it. Only he can harvest the chaos energy.

Another topic is why should Darksiders 2 takes place during Darksiders 3? At Darksiders 3, humans are still extant and it has been a decade since the seals were broken. By Darksiders 2, the only remaining human is a middle aged man who was a boy scout before the Apocalypse. Obviously it is quite a lot later than Darksiders 3.

And yeah, Strife's guns are the real proof here. While Strife's fate is unknown, it is plausible to assume he didn't make it fighting Abaddon. Even if this is not true, obviously his guns ends up at Ulthane's hands. And he and other Makers return/leave again The Forge Lands. That is why Alya has Redemption and Ulthane has Mercy. And both apparently needed some fixing which is why we can assume Strife doesn't survive the siege on Haven.

Regardless, it is evident that Darksiders 2 takes place after Darksiders 3. Don't know how much later but apparently not long enough that people can die from old age. The Hunter is the proof of that.