I think cross-play is broken and needs a rework.
When using a keyboard and mouse on Xbox, you should be paired with PC players. However, due to how cross-play was implemented before the Xbox release, some PC players won’t be able to be matched with you.
The thing is, in the general settings, there’s a nonsensical cross-play setting that lets you enable/disable cross-play between the Microsoft Network and Steam.
If a PC player has this setting disabled, then they won’t be matched with Xbox players using a keyboard and mouse because Xbox players belong to the Microsoft network.
This setting makes no sense now and should be removed. The only thing that matters is if both players use the same input method. The network they belong to is irrelevant.