Have you tried forgetting the watch from Bluetooth, deleting the Wearable apps data/cache, wiping your phone's device cache AND a factory reset of the watch? That should get you to a point where this works again.
I have tried all the above. I recently upgraded to Samsung A71 5G and my Galaxy Watch will not stay connected for more than 30 minutes max. It's becoming extremely frustrating.
I should probably update this thread. Basically, I factory reset my phone and reconnected my watch. After loading the backup, it gave me an option to turn off all battery optimization. However, the issue is still occurring. But this time, I am certain that it isn't the fact it isn't allowed to run. I believe the issue is now that it is crashing. I don't mind this because if I shut everything else on my phone off and I leave it on the wearable app, it doesn't crash. Still annoying but still