I'm struggling to understand how this is a bad look for Typescript. Do you mean that the specific choice of Go reflects poorly on Typescript, or just the decision to rewrite the compiler in a different non-TS language?
If it's the latter, I think the pitch of TS remains the same — it's a better way of writing JS, not the best language for all contexts.
I think a lot of folks downplay the performance costs for the convenience of a shared code-base between the front and backend.
If the TS team is getting a 10x improvement moving from TS to Go, you might imagine you could save about 10x on your server cpu. Or that your backend would be 10x more responsive.
If you have dedicated team for front and back anyhow, is a 10x slow down really worth a shared codebase?
If it's the latter, I think the pitch of TS remains the same — it's a better way of writing JS, not the best language for all contexts.