Unable to remove discovered WiFi networks on iPhone 15

Assuming you're an ISP technician like me, ever since the new iPhone software update my phone has been crashing constantly, especially when in the Wifi settings page. Like you, I've tried everything to remove the 1000 plus known wifi networks at once, including using iCloud Keychain on my Mac to remove them. This removed them from my Mac but still did not remove them from my iPhone, even after resetting the Network Settings. Currently removing them one by one from the Edit list in the iPhone Wi-Fi settings. What a pain in the neck, but it's going by quicker than I thought. Probably 10 minutes or so to do them all, way way less time than I've spent trying to delete them all at once to be honest lol ;). Apple if you're listening you've gotta fix this.

Hello RGL3, In Settings > Wi-Fi select Edit upper right of screen. The iPhone should Face-ID you or ask for a password. Then you will see a list of known Networks. and you can either delete by pressing the Red minus circle or press the Circle i button for more info on the network and at the top of this page you can select Forget This Network should you choice not to keep it your Known List.

RGL3, Understand. From what I've been able to find out the Network resets all settings to default except the Network Name and I think that is what you are seeing. The name is still there, but you have to manually put back in the password to rejoin a network. If you want to get rid of the networks name and all then you may have to do them one at a time for the results you want. There is a difference between Reset and Delete.

As your situation appears somewhat unusual, log some feedback with Apple, too: Product Feedback - Apple