Why was INSERT DELAYED deprecated?

https://dev.mysql.com/doc/refman/5.7/en/insert-delayed.html

I used to use it and it was incredibly useful.

I knew it didn't work with InnoDB, and I was using it back in the day with a MEMORY table. However, I didn't realize it was buggy and hacky all around. Oh well.

Hello,

From what I am reading it was upgraded for INNODB tables and replaced with
INSERT [LOW_PRIORITY | HIGH_PRIORITY]
If you use the LOW_PRIORITY keyword, execution of the INSERT is delayed until no other clients are reading from the table. This includes other clients that began reading while existing clients are reading, and while the INSERT LOW_PRIORITY statement is waiting. It is possible, therefore, for a client that issues an INSERT LOW_PRIORITY statement to wait for a very long time.
If you specify HIGH_PRIORITY, it overrides the effect of the --low-priority-updates option if the server was started with that option. It also causes concurrent inserts not to be used.