You forgot to mention: if you lose your keys, youre fucked. That is, of course unless you trust a centralized unregulated entity to manage them for you.
After explaining improvements to this specific issue, it still feels like way too much friction for the average person to deal with. I think there will be more improvements as time goes on but maybe that's just the cost of doing self-custody. In the end, I guess it's up to the individual to decide whether it's worth it or not.
Wouldn't it just require one to be hacked - where the risk is losing access to your wallet? Say an evil hacker destroys one of the halves of your private key, now the wallet is unavailable.
If the risk is - drain the account - then yes, both would need to be hacked in order to get access.
However, I'm sure the MPC wallet prompts you to write down your half of the key on a piece of paper during wallet set-up. That way if your device fails (or you cross fate with a particularly chaotic hacker), you can import your key into a new wallet.