The RTGs weren't launched in a different era. The most recent RTG went up less than three years ago. (On Perseverance.)

I stand corrected. I thought all the rovers were solar powered. My mistake.

Most of them have been, but Perseverance and Curiosity were exceptions. I believe the original motivation was for Curiosity to be able to land at higher latitudes.

Yeah, I actually knew that. Just had a brain wedgie/senior moment. (Seems to be happening more and more as time goes by. Funny how that happens.)