No they should absolutely not and the reason has nothing to do with the languages as such (which would be fine choices!) and all to do with people. A senior pro

No they should absolutely not and the reason has nothing to do with the languages as such (which would be fine choices!) and all to do with people. A senior programmer that writes Java or C# in 2021 is not going to jump ship from his comfy overpaid position into your fancy space ship. Why haven't you learned anything new?