Playing games, socializing, exploring, and creating are all highly engaging and help learn English online.
The optimal ratio of teacher talk to student talk--the students should do most of the talking.
The students must, therefore, speak English to communicate with each other.
The memory has an easier time recalling highly contextualized information.
For example, they are allowed to choose their topics, projects, locations, etc.
Unfortunately, many online education platforms do not require their "teachers" to have any teaching credentials. They simply require these "teachers" be native speakers of English.
You can’t expect highly educated and experienced teachers to design and teach an hour-long class for $10.00.