I've already started the project in meteor and although I like how quickly I can build a web application using it, I hate the fact that its so opinionated and now I'm wondering if I need meteor at all. Majority of my current code is meteor independent (I've written an API client class to use for an ecommerce backend) and I can easily port it to Express or other server-side nodejs framework.
Also the fact that the testing is cumbersome, and page size is already reaching 4MB even though I've hardly even completed 10% of the project.
So despite so many problems, and the fact that I don't require reactivity, is it worth using Meteor at all?
tl;dr: I don't require the major selling feature (Reactivity) of meteor, should I still continue using it? What nodejs framework should I use if not meteor?
This is a very subjective question; I'm not sure it meets the site guidelines. The answer will depend on several factors:
In your situation, I would be inclined to use Express instead. Meteor is great, but Express is more stable, has a larger ecosystem, and is much more flexible. It's also based on an older, more established paradigm (similar to frameworks like Sinatra) which will be more familiar to any other developers that need to touch the project in the future.