The word borchu is loshon tzivui. He is instructing the listeners to “bless” Hashem. Since “blessing” Hashem means to recognize and declare that He is the source of all blessing, it follows that “borchu” means that.
(Perhaps I should have written that the translation is to “declare” (rather than use the word “recognize”) Hashem as the source of all blessing
I say “Bless you good L-rd” about 100 times a day. Is that wrong to say? First of all, using the L word even though it’s actually a blessing, second of all, is it wrong that I bless Him and not say He IS blessed? Just thought I’d bring it up because I really do say it about 100 times a day.