wax作动词有上蜡抛光的意思,在这里wax lyrics表示赞扬或美言的含义
朗文当代英语词典
wax lyrical etc about
to talk with extreme feeling,liking or pleasure about something - used humorously
例句：Journalists wax lyrical about the band.
wiki
wax lyrical
To talk about something with much interest or excitement; To become,or tend to become lyrical
to talk with enthusiasm and alacrity using well chosen words.
To praise something or someone.
It means to talk positively about someone or something.
这些来源都可以作为佐证