It's been quite a while (several years) since I read the original paper [1] on RISC-V's design but I remember it being very elegant, with a lot of things fixed that other ISAs have been stuck with for decades. It's truly modern in the sense that it demonstrates how much we've learned in the last few decades, without being such a radical departure that it requires rearchitecting all software for it.

[1] https://people.eecs.berkeley.edu/~krste/papers/EECS-2016-1.p...