There's actually a relatively new alternative to Meteor called Meatier. The reason why this project was created:
Meteor is awesome! But after 3 years, it's starting to show it's age. This project is designed to showcase the exact same functionality as Meteor, but without the monolithic structure. It trades a little simplicity for a lot of flexibility.
The project provides a nice overview of differences between Meteor and Meatier and explains why. There has been a discussion going on at Crater.io to ask the opinion of Meteor developers, which is worth to check out as well.