It is like with all development efforts: what are you planning to do?
We use Meteor, because we need the reactivity in a classroom environment so we can provide a learning process that goes beyond behavioristic models. This is from my research perspective impossible with any other framework.
If we have another use case we may use a different framework but if there is a DB required and accounts, code splitting etc. I will still use Meteor because this is all there without any extra integration.
Regarding scaling: If it does not scale it is usually your app architecture that prevents you from it. If you target 10000+ users you will have to make distinct changes what when and where to subscribe, stop, oberserve etc. and this takes time and effort. Do other “reactive” frameworks eliminate this process? I highly doubt it.