Nobody on the Internet can send a packet to an internal IP on your network except for immediate L2 neighbors (I.e. your ISP).

Symmetric NAT 100% stops inbound unsolicited connections to the public IP. And using the public IP is the only way 99.999% can address you.

I implore you to write down (even if just for yourself) what the packet headers would be for you to get a packet from Starbucks WiFi to the device at your home at 192.168.0.5 that has made no egress connections.

You’ll quickly find what you’re suggesting is nonsense. port address translation requires an entry to function. It’s not some optional security feature. It’s required information to get the packet header rewritten to reach private devices.