Why does Thanos's gauntlet look destroyed after he used it at the end of Avengers: Infinity War?
As Eitri defines the gauntlet as 'a device capable of harnessing the power of the stones', it actually stands up to that, but please note that the Infinity Stones are depicted as the most powerful entities there are in the MCU.
It shall be no surprise seeing the gauntlet decay after using up its full potential, viz not only keeping all stones together, but using them ALL at a particular instance.
Also, it's not right to comment until seeing Avengers: Endgame whether the gauntlet can be used again or not.
The Gauntlet acted as a conduit for the Infinity Stones. The scope of the Decimation exceeded the conductive capacity of the Gauntlet and burned it out. This would be similar to how a conductor would burn up if too much current was passed through it.