Meteor is monolithic in that it forces your app to be structured in a particular way - It dictates how you should handle your data and how your scripts get loaded/bundled into your app. That said, I think it's much more flexible (and scalable - In a business sense) than a closed solutions like Firebase. I think Meteor is suitable for most projects and monolithic isn't always a bad thing - There is some negative stigma around the term but it's not entirely fair. People don't go around calling Linux 'monolithic' even though it is!