Oh man, also a late newcomer to this thread. There are many things going on which are being connected, when a connection is not necessarily there.
IMHO, let's break it down:
1) the second class status - e.g. calling Crown Heightsers "farmers" - of non Shluchim
This is absolutely an issue. It is not something derived from the Rebbe and is something that should be abolished and obliterated.
2) limudei chol for kids
The Rebbe clearly voiced his opposition (see sources upthread) yet the Rebbe didn't disband ULY, and continued to encourage other schools to open with limudei chol (albeit with conditions, such as beginning in the morning with the kodesh). To say the reasoning was only to attract outsiders is a stretch. There are many cities that 2 schools could have been opened. And the Rebbe doesn't seem to explicitly offer that "excuse" - to my knowledge. One might even conclude that OT is the exception, not the rule.
3) mesivta - high school education
I don't have much knowledge about the Rebbe's view about this as separate from kids Chinuch.
4) liberal arts College education
This was an unequivocal no from the Rebbe. The only exceptions I have heard, in this thread or any other place, were those who had already begun studying. Of those, there are dozens of people the Rebbe told to complete their studies, and even pursue further studies including PhDs, etc.
5) vocational studies
Studying a specific secular subject for the purpose of parnassah is entirely different to just "getting a degree" and something the Rebbe was more supportive of.
Incidentally, in "Rebbe," which I just read, Telushkin does a pretty good job detailing the Rebbe's nuanced view on college education.
Age and stage of life is also a factor.
6) the ability to earn a living without secular education.
I know of people who have become lawyers, accountants, and doctors after completing the system.
The numbers of people who work in fields entirely different to thesubject of their university degrees is huge.
I earn a living (in not exactly flush, but thank G-d, I get by) as a writer (in English) having learned English and math up until 7th grade. I know this comment isn't exactly the best advertisement, but I'm writing it on glass with a thumb, I'm not going to correct grammar and spelling.
Ime, there is no correlation of success of lack thereof between people who graduated the system without secular studies and those with diplomas and initials. Obviously I've never conducted a survey or study, but that's my feeling.
Regarding the Shluchim using bad English (my target market as a writer ☺️) - again there is no correlation between good English and success. One Shliach I know makes the most hilarious speeches, quotes of which have become part of Chabad urban legend (extinguished guests, for one. My personal favorite: on the phone with a customer service rep he said, "Y as on Wyoming").
His community is one of the most affluent in the country, he speaks before multi millionaire businessmen and professionals, and they couldn't give two hoots. He is as truthful and warm a person as there is, and that's all they care about. Good English they can get from their secretaries. I went to a funeral he lead, and I struggled to hold in my laughter at some points. The family couldn't stop thanking him for the beautiful job he did.
As an aside, my bona fides for the above:
1) My parents are Shluchim. My in laws are Shluchim. I never dreamed I'd do anything else but shlichus. I still hope to, but like Facebook says, it's complicated. There is no bitterness or jealousy behind my comment.
2) my father was one of the the first students in Oholei Torah. My grandparents were moser nefesh to send him there. The passion for chinuch al taharas hakodesh with zero limudei chol runs deep in my blood. Yet one cannot ignore the other facts on the ground.
4) one of the more famous sources of the Rebbe explaining his opposition despite his studies in university, (just because one person jumped into a fire and came out unscathed, doesn't mean anyone else should jump in) was told to my grandparents in a yechidus.
Anyway, where are you going for a chol hamoed trip?