How about inserts suck in general for parting? Carbide needs to run on a precision setup, from bearings to floor bolts- it hates intermittent loads, interrupted cuts, tool chatter, and spindle vibes. Carbide is nearly hard as diamond, and shatters like glass when flicked with a finger.
M2 and Cobalt are okay for parting, but even they are a little too brittle.
For many years before high speed machining, T15 was the go-to for parting tools. It's a tungsten precipitate steel, not a moly/tungsten like HSS, and it is true to toughness rather than hardness. These tools cut and don't break. You can burn them, like every other material but carbide, but they are easily retouched with a stone or bench grinder. But they don't shatter or explode, which I find nice.
Carbide is not always the best choice. It is usually the most expensive choice, though.