You spend 10 times more time writing so much more code having to make the UI 'react' to the changes that you wish to see.
With React/Vue/Angular it's just a case of adding a conditional.
With jQuery you've gotta do something like
jQuery('.this').hide();
jQuery('.that').show();
jQuery('.thisotherthing').show();
Gets really confusing, hard to test and hard to maintain.
Then when you want to do things with fancy selects and dynamic option choices and all that good stuff it just gets even more unruly.
With modern JS frameworks you declare a state and your UI reflects your state. Rather than with jQuery having to manage both the state and the UI all at the same time.
I'm forced to use nothing but jQuery at work so I'm quite competent with it so it's not from lack of experience. It provides nothing but pain and misery.