You might be much more experienced than me so feel free to discard my suggestions if you objectively know you're right. However, I would strongly disagree with

You might be much more experienced than me so feel free to discard my suggestions if you objectively know you're right. However, I would strongly disagree with you on the part about it not being suitable for complex applications. If you feel that way, you can choose to have a decoupled backend (which is what I do with Django) or go all in with full-stack integrations (tRPC in conjunction with edge functions) on top of Next.js. I have seen great apps built with both of those ideologies.