If this actually is true, something big must've happened for Joy Reid of all people to get her show cancelled.
Still, I'm gonna take this with a grain of salt until more information is available.
Joy Reid was a useful idiot to screech over-the-top takes about Trump as a bLaCk wOmAn. Trump is no longer in the spotlight, and news channels are doing poorly in the ratings, meaning their available cash is shrinking (or about to shrink). She probably has a relatively pricey contract from being on the air awhile. If there's a convenient way for them to jettison a costly, burdensome contract, they'll do it.
Rachel Maddow brings in an audience of >1m when her show comes on. Joy Reid either doesn't move the needle or perhaps loses viewers. Rachel is worth a LOT of money (and is paid accordingly). Joy Reid may have negative value.
Never mistake pundits for sacred cows, they're tools for profit. If Joy is bringing down profit and costing them a premium, she'll disappear into the ether. If so, good fucking riddance. Maybe she and Keith Olbermann can partner up and tard rage into the void, because it sure won't be to an appreciable audience.
EDIT:
Holy shit, it's MUCH worse than I thought. Look at the table in this article -
Cable News Ratings, Wednesday January 5: Ari Melber Beats Joy Reid on MSNBC
The shows before and after Joy Reid draw about 1.47m, but viewership dips to 1.28m for Joy's show. Her hour is
costing them about 200k viewers or ~13% of their audience. She's in a world of shit.
Note that it also shows the ~1m viewer bump that Maddow provides, which is why she's valuable.