VM -Your premise is wrong to a certain extent. Obviously there are always Ledegayers who don’t want to work and sit in a Yeshiva and do nothing, but I think this is a small amount of people there. They don’t have much influence on the Yeshiva in general.
What you don’t understand is that R’ Aharon Kotler zt’l brought the concept of learning Lishma to the US. So now we have very capable & bright minds learning all day without becoming Rosh Hayeshivos, Rosh Kollelim or Rebbeyim. This is a purpose in of itself. I think people leaving Yeshivos nowadays has more to do with not making ends meet, than with Zitsfleish. So a lot of these people without s/o to support them are intelligent and find fields that they would be good in.