IMHO, there are two different parts to yeshivish. The first one is halachic yeshish; spending excessive time learning, keeping many chumros, etc. Not only don’t I see anything wrong with this, but it think it’s a very good an praiseworthy thing.
Then there’s the culutral yeshivish; a certain mode of speech, dress, etc. While I do not see anything wrong with this, I can understand why some people might not like it in excess.
mw- i agree with what you wrote. i also believe that some people don’t like the 2nd, but the 2nd is like you said, cultural, like the Amish. it’s not a statement as to how much yiras shamayim they have or how much they learn, but it does serve a function. it keeps these guys – some of whom may not be able to learn 12 hours a day, under the realm of good peer pressure. meaning, because of cultural and/or peer pressure, these guys do not watch movies, talk to girls, see things they shouldn’t be seeing, etc.
and as for both groups, people tend to think that both groups should have perfect middos. that is, if they dress and talk yeshivish and/or if they learn a lot, they should already be perfect. that would be nice. but shouldn’t people who don’t have the best of middos also learn. maybe through their learning (and from my understanding, this is so), their middos improves. so, they may be far from perfect; but, could be, that that same person if he became a lawyer instead of learning, would have even worse middos.