From what I've read, it's an accumulation of small details.

I have a pair of Soundcore buds, and they work well. Unless only one of the two decides to not connect to the phone. Or they randomly decide to change the noise cancellation setting. Or their gesture detection randomly triggers. To be fair, it's pretty rare and easy to fix: put them back in the case and back out, etc. But it's small things that remind me "yeah, I did not shell out for AirPods". (also, their transparency mode for conversations is nigh useless, but it may be because those are a 4 year old model).

I regularily use a pair of Sony headphones too, and they are a bit less troublesome, because it's a much simpler product: a single BT connection, physical buttons for some quick controls, etc. But they still have their warts: can't charge and be used at the same time, handoff between two source devices still don't work after years, etc.

It's an accumulation of details that are not big, happen rarely, and don't need much to get used to. But they still need to get used to.