It is harder to do more with less. There is a reason React and other is used so much. Makes it easier to make interactive websites. It’s like asking why backend engineers think it’s harder to code an api using C instead of using Django.

I used to think that was true but I now think it’s only true for very interaction-heavy apps: if you have hundreds of interactions on a page over many minutes, using an SPA is amortized across a lot of time, but if it’s something you could do with e.g. a simple Django app you’ll not only be done faster but will spend an order of magnitude less time on maintenance and accessibility work.