Martini vs Spring

Is learning Spring and Spring Boot for web apps back-end development is still relevant in 2021? Feel free to share your views with comparison to Django/Node.js/ ExpressJS or other frameworks.

Please share some good beginner resources to start learning about spring/spring boot framework to build the web apps.

So currently I have experience in Node.js, but just to expand my stack knowledge and for getting backend developer roles, I thought of learning another backend-related language/framework. I have heard about Django, Golang, and Spring. I am mostly trying for backend API roles, and far as I've heard, Django REST framework can be a pain to work with. I've heard there are issues with Golang for package management (like how recently the Gorilla web toolkit is archived) and as for Spring, it's a vast ecosystem to learn so not sure if it's worth investing in. I would like to know which tool/framework to learn, which can help me get high-paying jobs and has a lot of scopes, and also which is great for making REST APIs. Any other tool that can do the job better than these three is also welcome!

I am provided with the opportunity to learn one of these technologies during my training. I have prior experience with Spring and found it tough and still haven't figured out when to use what annotations among the thousands of annotations provided. On the other hand, I am very proficient in Java data structures and algorithms (custom comparators, etc.)

I have used Node.js and found it interesting, but I am wondering If I am taking the risk of choosing a framework that has a comparatively lesser scope in the future. One advantage I see with the node.js is the number of tutorials available and the ease with which I can code.

Please recommend which path to take. Is Spring learnable, or should I spend my energy on learning Node.js instead?