It almost goes without saying that Wear OS is not developing as fast as we had hoped. Let’s say it anyway, though. Google has been slow to add new features and even had to roll some changes back in the developer preview. There’s also at least one bug that has plagued users for months. Since late 2017, many users have been unable to route call audio through their watches. Even having the feature enabled breaks call audio. There might be some progress in the latest Android P preview, but many say things are still busted.
You are supposed to be able to transfer call audio between the phone and watch (with a speaker) by enabling the “Play phone voice call on watch” feature. However, Wear OS users have been complaining for months that doing so causes audio to cut out for 10-15 seconds whenever a call is placed in an app that supports Bluetooth (e.g. phone, Duo, WhatsApp, etc.). The lag happens no matter which device is selected for audio output. The only solution is to disable Wear OS call audio entirely. Well, or disconnect the watch and leave it in a drawer someplace.
A Googler started working on this bug in December of 2017, and dozens of users have chimed in with details of their own issues. Most people appear to be using Pixels, but there’s a smattering of other phones like the Galaxy S8 and Xiaomi MI6 as well. There’s probably something wrong on both the watch and phone side that contributes to the problem, which is why a few people report the bug is fixed in Android P DP3. Others say the bug is still present.
Basically, this is a giant mess that should have been fixed months ago. If Google cared about Wear OS, it probably would have been.