Some of it is the constraints with the main use cases: low power, (relatively) high bandwidth, the need to pair devices without screens. Comparing this use case to something like wifi is unfair.
A lot of it is due to backwards compatibility. Bluetooth isn't simply bluetooth. There are different versions, different profiles, different codecs, and even different optional features.
The two devices being paired have to figure out what version/profile/codec to use to talk to each other, and gracefully fall back to the lowest mutually supported featureset. This is a really hard problem, and the devices don't always handle it well.
A lot of it is due to backwards compatibility. Bluetooth isn't simply bluetooth. There are different versions, different profiles, different codecs, and even different optional features.
Have a look at the matrix: https://www.rtings.com/headphones/learn/bluetooth-versions-c...
The two devices being paired have to figure out what version/profile/codec to use to talk to each other, and gracefully fall back to the lowest mutually supported featureset. This is a really hard problem, and the devices don't always handle it well.