Disclaimer: The foregoing is my basic impression of the topic, but I am not yet strongly opinionated about it.
Today’s Charedi Torah greats generally oppose the idea of secular studies in yeshiva, certainly for the majority.
But anyone who knows history is aware that the idea of combining secular studies and Torah learning is not new. The Rishonim did so, and so did other various generations. And it worked just fine. Does this mean doing so is a good idea today? Perhaps not (we hope to explain why elsewhere). But the Chazon Ish writes in Kovetz Iggros 3:
מנויה וגמורה בסודם של רבותינו גדולי הדורות שלא להרשות לימודי חיצוניות לבני הישיבות בזמן שקידתם בתורה בהתלהבות נעורים…
The plural “Doros” seems inaccurate.
Everyone knows the story of the Chafetz Chaim baring his heart when asked for the source of his prohibition on studying languages in Yeshiva. But now you know why he needed to be asked in the first place, and why his unique response was the only appropriate one.
And the matter of married adults is a separate one.