Inserts in MySQL 8 are slower than Inserts in MySQL 5.7

A difference between 5.7 and 8.0 is that binary logging (to be used for replication and PITR) is on by default in MySQL 8.0. To run without binary logging in 8.0, start the MySQL server with --disable-log-bin.

More details The Binary Log

The binary log contains “events” that describe database changes such as table creation operations or changes to table data. It also contains events for statements that potentially could have made changes (for example, a DELETE which matched no rows), unless row-based logging is used. The binary log also contains information about how long each statement took that updated data. The binary log has two important purposes:

• For replication, the binary log on a master replication server provides a record of the data changes to be sent to slave servers. The master server sends the events contained in its binary log to its slaves, which execute those events to make the same data changes that were made on the master. See Section 17.2, “Replication Implementation”.
• Certain data recovery operations require use of the binary log. After a backup has been restored, the events in the binary log that were recorded after the backup was made are re-executed. These events bring databases up to date from the point of the backup. See Section 7.5, “Point-in-Time (Incremental) Recovery Using the Binary Log”.