Precisely the same issue here. MacBook Pro 2019 2,3 GHz 8 Core Intel with 32 GB DDR4 and Mac OS Monterey 12.1 was crippled after the latest update in all connectivity issues (Safari, Mail,Messaging), besides RDP-connections to my local network which which slowed a bit but remained usable. By deactivating the realtime scan the performance is back and lively.
So id do think there is an compatibility issue here with the latest Monterey update.