Is it common that my work is wasted since a collaborator who is the first author does not submit the manuscript that I have worked on? I am a postgraduate student at a research-oriented university. I had spent about 2 months to work on a project. I collaborated with another postgraduate student who is the first author.

In the project, I mainly contributed to the paper writing such as whole parts of introduction, background, related works, discussion, and conclusion. Also, I wrote some subsections in the main body and made most of the figures and tables in the paper.
So I think I put a decent amount of time and effort. 

But my collaborator wants to discard this paper since he/she thinks the methodology of the paper is too outdated and thus it cannot be accepted for the top journal/conference.

It seems my 2 months of work is wasted. What do you think about this situation? and What should I do? 

Thanks in advance for any thoughts and advice.
If your contribution is just to the writing and not to the underlying research then you don't have much invested. However, if it helped you improve your writing skill in any way then it isn't wasted. 

But the best way to capitalize on it directly is to stay with the project if it continues but get more deeply into the research behind it. 

But don't minimize the impact of the experience. Think of it as an investment that will only pay off longer term. I assume the first author also put a lot into the work and is a bit disappointed also. 

But you should verify everything with your supervisor/advisor. Perhaps the other student is being overly pessimistic. 

OTOH, discarding work partly done is common enough. Not the norm, perhaps, but sometimes you need to get fairly deep into it to learn that there is less there than first anticipated.