When you are in a little town in Poland with no electricity or running water, fewer social interactions and obligations, and no non-Jews to deal with, it is easier to go back to shtetl life.
Today, it just doesn’t work the same way, for many reasons:
1) Earning a living today requires us to be involved in secular society. This, in turns, affects the yeshiva system.
2)Niskatnu Hadoros
3) Back in the old shtetl days, nobody had “secular” studies. If you were good at chopping wood, you became a woodcutter. If you had deft hands, you could be a tailor. If you were ambitious, you were a merchant. Today, you must know proper English in order to pass a driving test, serve in jury duty, register to vote, and a host of other things that are vital to today’s life.
4) There were no cars back then, which made it easier to and learn all day, because there was nothing else to do and no other place to go to.
And a host of other reasons.