It's just a disconnect. The circuit is correctly protected with a 200 amp fuse. I looked at the wiring. It's correct.If the switch is just used as a service disconnect bigger is fine. If it's used as circuit protection you're right you shouldn't go up. dlj the circuit is fused at 200A, so that's what's providing the overcurrent protection, and the switch should be rated for at least that much.
Whether the 200A fuse is really the right size for the wiring in the circuit is a whole other matter. Maybe worth a quick look at the wire gauge to make sure it's adequate and all matches up.
I do not need the disconnect to be protecting the circuit. The fuse is there for that. I sure don't need that switch to be melting in the circuit as it's running, what it has been doing currently (no pun intended). That is a fire hazard!
dj