fwiw i've never experienced the drawback of separate languages for server and client. nor did i ever experience the benefit of single language across server and client.

being forced to use javascript on the server sounds like a cruel joke vs a benefit. I mean just simply from "i can literally pick anything for my controlled server env" vs "no we're a js shop cuz web"

edit to add: is it one repo? or maybe shared types. typescript is probably the strongest argument. can enforce integrity truly across the stack. but i don't think that's worth being forced into js environment and packages. community is forced to reimplement everything in js. no good.