Monster Hunter World is a stupendous game that has been a great success already, with 5 million units shipped worldwide, and a Metascore of 91- and yet, if you are on Xbox, you’re going to find that a significant part of the experience is unavailable to you. For some reason, matchmaking on the Xbox One version of Monster Hunter World is completely borked.
The issue is so bad that Capcom has acknowledged the issue from the official Twitter account for the series, noting that they are looking into fixing it. Meanwhile, they recommend you either team up with friends directly, use Session IDs, or use the LFG group on Xbox One if you want to play with randoms.
Those workarounds are appreciated, but they are just that, workarounds- hopefully, Capcom fixes the online mode on Monster Hunter World soon. For a modern game of this stature to have these kinds of issues is not a good look.