Is jQuery dead?
Query isn't going to go anywhere until businesses can realistically assume that the vast majority of their customers are on modern browsers. So it might be dying, but, much like Adobe Flash, it's going to be a slow death.
I see jQuery mainly as syntactic sugar and cross browser normalizing lib. It also does some clever behind the scenes grunt work such as removing data and event listeners from removed elements etc.
It's very useful depending on what kind of stack you're working with. I render everything serverside and then manipulate the dom manually, so jQuery provides lots of value for me. If I was working with something like React, there wouldn't be any reason to include it. As I said, dom manipulation is easy. It's like laying bricks at the construction site. Software architecture is the hard part.
Many developers are condescending to people who use jQuery. jQuery users are often seen as "lesser" developers. Ignore that. jQuery is just a tool, nothing more. It's also super popular and yes, most of the people who use it arent great developers. Just like most of the people who eat pizza aren't geniuses. That doesn't mean that everyone who eats pizza is a retard.
TL;DR - Get familiar with and try learning the native DOM api, but don't be afraid of using jQuery if it provides value for you, ignore the haters.
It's not dying. It just doesn't fit into the current thinking that manually manipulating the DOM is bad. At it's core, it's a convenience layer for doing something that Angular, React, et cetera obfuscate away completely.
You'll see Bootstrap mentioned in a similar capacity these days, although not as frequently, as people begin to adopt CSS frameworks like Inuit, Susy, Bourbon, et cetera that leverage a different approach to providing the same kinds of features.
Neither one is dying, or even remotely close to going away. But if these trends continue, they'll continue to become less popular for new projects.