None of my Bluetooth devices work with iPhone 11 since iOs 15.2 update. How do I downgrade?

I’ve reset network connections, erased content, turned Bluetooth off and on etc but my iPhone 11 cannot sustain Bluetooth connections or consistently detect devices since I’ve updated my iOS. I thought the latest update would fix it but it didn’t. I’m really frustrated and considering leaving apple after more than a decade with them. How can I get the old iOS back? It’s ridiculous to expect every other device to have a software update or be reset to work with this iOS but for the record I’ve restarted them all - fitbit, Tozo earbuds, Alexa