The only ignorant answer i’m seeing is from yourself.
The headphone jack is an inexpensive small connector that offers far better quality than bluetooth does (i.e. lossless audio), is universal and is a really inexpensive feature to add to a device.
The ONLY reason it has been removed is to push the sales of wireless headphones and earbuds. Fairphone got rid of it and soon after started selling bluetooth devices. And you just bought the marketing. As for the usb adapters, those are an extra point of failure and easy to misplace.
For all the good things Fairphone did, this is a really shitty one. If Sony can keep the jack on all their devices, anybody can, and the rest are excuses.
You don’t like the jack? You can just keep using bluetooth.