why as Jews, we do not proselytize to gentiles?

I heard in a shiur: "As Jews, we do not proselytize to gentiles, nor seek converts." My question is: why? What is the source of this prohibition? What are the reasons?

As opposed to Christianity and Islam who both want to convert everyone, Judaism is contrarily extremely tolerant towards other monotheists in general and aren’t interested in the least in converting anyone to Judaism! The reason is simply that every group is important to the harmony of the world. Just as Kohanim can’t be Levi’im, and also regular Yisraelim should be satisfied with their important role, similarly there is a beauty in manliness, as there is in femininity, and each role is unique and necessary. There is a necessity for gentiles and they have an important role, and that’s why we aren’t interested in them converting to Judaism and even try to persuade them to change their mind (the source is Yvamot 47a and Rambam, Isurei Bi’ah ch. 14). Only if they are really adamant in their sincerity we would allow them to convert, and then they are 100% Jewish, because Free-Will is also an ideal!