Large teams cannot deliver anything quickly. There is too much internal communication drag. The entire point of working this way is rapid feedback. Too many focus on the mechanics Scrum teaches instead of the goals. The problem you're seeing with small teams is the same problem you see when people decide to build microservices without any understanding of DDD. Lacking any focus coupling issues, they create a distributed monolith. Same with team structure. Because they don't focus on decoupling the teams, they have one, giant, badly communicating team and then try to manage those dependencies with something like SAFe. Small teams can accelerate feedback loops if the architecture is also improved to decouple the teams. Starting with small teams to build something new is easier than refactoring the org and a legacy application, but I've helped with the latter, and it's dramatically better than the alternatives.