Shopify Developer here (opinions are my own) we are running Ruby on Rails (obviously) and we do well with it. It's fast to develop, fast to deploy, fast to test. I have no complaints with it. I would say my gut says that there are fewer bugs, fewer issues, fewer on call incidences, less downtime, and faster development speed than when I worked in a Java shop with micro-services and serverless and plenty of modern things. Technical culture, discipline, quality of engineers and leadership matter so much more than what your tools are imo.