Synchronous does not mean 180 minutes of the teacher giving live instructions while the students are forced to be in front of their screens. It can be (especially for elementary) short chunks of lessons or assignments before breaking off to do them. The teacher can check in individually or in small groups with the students as they go along.

The asynchronous part of the day is assignments or activities they can do on their own but the teacher is available to the students during this time, same as if they were in person.

Just sounds like the teacher might not know the best way to run it, and it sounds like it's probably too much content for the day.

I just started teaching highschool virtually today for the first time. We did just about an hour long meet worth of content (lesson and assignment overview), then a 10 minute break, then a kahoot review. They broke off to do their work while I checked in.

Obviously this would have to be adjusted for elementary. Everything just needs to be short chunks of work, and parents also need to understand that they can't expect their kids to sit in front of the computer and be engaged and entertained all day long.