This is correct, we no longer include it in Admin Tools for Joomla 4.
This feature was very important around Joomla 1.5 when Joomla was still using the MyISAM storage engine for its tables. On busy sites you might have concurrency issues or crashes which led to the MyISAM data on disk to become corrupt., needing a repair. Moreover, the way it worked would create a lot of holes in the data file when deleting a lot of records, necessitating the optimisation of the table (pretty much like you would defrag a hard drive).
Joomla 4 —in fact, since Joomla 3.4 or thereabouts— uses the InnoDB storage engine for all its tables. Instead of using one data file per table, it uses a shared file across all tables. MySQL's repair statement does nothing on InnoDB tables as per https://dev.mysql.com/doc/refman/5.7/en/repair-table.html. Likewise, optimising the table will have probably no effect unless there is a full text index (of which Joomla uses none in its tables) and even then MySQL can be configured to do this automatically as per https://dev.mysql.com/doc/refman/5.7/en/optimize-table.html.
This means that the repair and optimise feature was doing absolutely nothing for the last several versions of Joomla and had no reason to exist anymore.
Nicholas K. Dionysopoulos
Lead Developer and Director
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