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”.