I'll add my 2 pence for why Rails is still suitable for startups. Rails is still the best framework for building web forms quickly. Web apps are mostly web forms. It helps you get going with everything ready for you (validations, style, views, etc). If you follow the conventions, you get a significant boost in productivity. I see people using other "modern" frameworks where they build api+validation, frontend+validation etc it is just a waste of time. Build the product, get it out there.