>If we are all supposed to be talking to agents now, what's the difference[...]?

it's a little cringe, but arguably the benefit of having agents use rails would be tht when you review and audit the agent produced code, you review something that is, as you put it: "beautiful and simple code" and "making it easy to reason about..."

I loved rails back in 2017. I may be an outlier but the line tempts me to try it again despite having adopted the who cares attitude to langs. Would be nice to hear from someone first hand if they felt it helped.