Basically when Halo Infinite opens, the crew of the UNSC Infinity been fighting Cortana's Created faction and the Banished for 2 and half years, cut off from Earth after Cortana and her Created EMP'd Earth at the end of Halo 5 and took control of the planet. They did manage to get new Armor about 3 months into the conflict, MJOLNIR Gen 3, which was created with numerous improvements, including the new SPIDR AI counterintrusion program, which was designed to prevent Cortana's created AI faction from hacking into the MJOLNIR armor's BIOS and taking control of the armor, but when the game opens that "new" armor is about 2 years and 3 months old, hence why John's armor has significant battle damage, scoring from Banished plasma weapons mostly. Likewise the UNSC weapons that John will be using in the campaign are left overs on the surface of Installation 07 from a battle that the UNSC lost on the ring about 6 months earlier, so they have 6 months of weather damage presumably.
That makes sense. Thanks for the background, I still have yet to play Halo 5's campaign and I sometimes lose track of what is going on in the larger scheme of things.
...to avoid getting banned for inactivity, I may have to resort to comments that are of a lower overall quality and or beneath my moral standards.