Obviously, if jQuery is still your jam in 2019, that's your decision and no one is going to force you to stop using it. The approach Bootstrap is taking is interestingly backwards compatible in that the updated plugins will still register their previous jQuery APIs, even if their actual implementations will now be "vanilla" JS directly against the modern browser APIs.
If you're making an SPA, then jQuery is a bad choice for many reasons. jQuery is just a DOM wrapper, and doesn't give you any application structure, which tends to lead to pretty messy applications.
What I want is just intercept some (but not all) form submissions and load the results via AJAX, and such.
Here's a simple form example:
Anything more 'rich' gets confusing very, very quickly and with how accessible Vue/React/Angular are it doesn't make sense to use jQuery.
JQuery modifies the DOM at runtime, this means lots of node traversals and redrawings on the fly, which make it nearly impossible for the Javascript engine to optimize anything.
More modern frameworks in general use the concept of a Shadow DOM: they keep their own representation of the DOM internally and only send the full frame to the engine for rendering. It seems to be extremely more efficient and flexible.
That’s not saying don’t use a virtual DOM but pick it knowing that you’re taking on a moderate degree of inefficiency in exchange for a better coding experience, consistent structure, etc.
Thankfully there are still places that will see past that. Still, the idea of "keeping up" does need to factor in, and the experience could serve as a wake up call to where the industry is headed.
New frameworks reflect how developers think. Sites want to work more than they want to look unique. In many cases, uniqueness is viewed as driving up training or onboarding cost.