Why? What has been stopping you? I think this is an important question.
but web3 projects are build upon mostly react and next.js
Whatever I may personally think of "web3" I dare say React isn't a key component of it. Those projects use it because it's currently a popular and prevalent skill set so the choice of React is purely incidental.
Learning React and Next.js isn't going to give you the key to understanding "web3"—you will simply become more familiar with React and Next.js. Is it still useful to learn? Yes provided it is useful to you in some way.
I am good at JS and Angular 2+ framework
Right and using React will feel quite a bit different; it will introduce you to a different way of building SPAs (though there are typically two different design philosophies at work). Knowing React means you can collaborate with other React developers in some way—maybe that is what is important to you.
Just keep in mind that React is just a tool; it's good for some use cases but has limitations like any other tool. So having a particular goal in mind where the use of React is relevant is probably a good idea to keep you motivated while you learn it.
Too Late?
jQuery was released in 2006. In the 2020 Stack Overflow Developer survey it was still the most commonly used web framework; in 2021 React finally surpassed it.
jQuery was found on top 8041/10k, 83432/100k, 794769/1m live sites.
React was found on to 4423/10k, 28509/100k, 149547/1m live sites.
Why? What has been stopping you? I think this is an important question.
Whatever I may personally think of "web3" I dare say React isn't a key component of it. Those projects use it because it's currently a popular and prevalent skill set so the choice of React is purely incidental.
Learning React and Next.js isn't going to give you the key to understanding "web3"—you will simply become more familiar with React and Next.js. Is it still useful to learn? Yes provided it is useful to you in some way.
Right and using React will feel quite a bit different; it will introduce you to a different way of building SPAs (though there are typically two different design philosophies at work). Knowing React means you can collaborate with other React developers in some way—maybe that is what is important to you.
Just keep in mind that React is just a tool; it's good for some use cases but has limitations like any other tool. So having a particular goal in mind where the use of React is relevant is probably a good idea to keep you motivated while you learn it.
Too Late?
jQuery was released in 2006. In the 2020 Stack Overflow Developer survey it was still the most commonly used web framework; in 2021 React finally surpassed it.
React is often called the modern jQuery or PHP.
React was released in 2013 so it probably still has a few years to go.
Though sometimes results can surprising:
Meta/Facebook is reportedly still using BigPipe (i.e. React isn't a one-size-fits-all solution).