The problem is that statement is completely ignorant of the audience. An engineer might understand "jquery" as an explanation for slow delivery speed, but it is

The problem is that statement is completely ignorant of the audience. An engineer might understand "jquery" as an explanation for slow delivery speed, but it is not the right explanation for the standard exec (notice that you inferred a lot of information from that statement that someone unfamiliar with front-end technology would not). What the exec needs to hear is "this is built on out-of-date technology that is slowing us down and to fix that we need to be given time to migrate the application to a modern technology". Problem + proposed solution + no irrelevant details like the name of the technology.