I am about to complete my graduation with a computer science background. I want to pursue my career in software development. My front-end knowledge is very poor. I didn't like PHP so I didn't go for Laravel. My university offers a course on ASP.NET, I liked C# that's why I took asp.net. But now I think .net tech is unnecessarily complicated and most of the job offers available for .net are not for freshers. Should I try js and Node.js now? I mean as a fresher which tech stack should I choose for web development(Backend)?
.NET is an old experiment in using a markup language to separate the UI from the business logic. The idea was that this would allow a small team of hyper-competent engineers to build the tooling and code for a large team of less-skilled front-end developers to leverage. In practice, leveraging that customized UI markup requires understanding and adjusting the underlying code. The result is that any UI change requires a hyper-competent .NET engineer.
However, many larger companies bought into it a long time ago, and now have a hard dependency on old monolithic .NET ecosystems, and they do need .NET developers to maintain them.
So, you can get a well paying .NET job without much difficulty. However, you'll neither like it, nor be doing anything interesting. There's no growth here, only a very long slow death of .NET (that'll probably take another 20 years).
What I can see, you are confusing yourself, if you studied .Net now it's better to work as .Net developer, and you will find opportunities as fresh. Just search and don't waste your time. After you get more experience in .Net, then you can learn NodeJS if you still need to learn it.