> However, its early days.

Theia has been out for eight years now,

Came out of beta less then a year ago. What I mean is adoption is slow (if even there), so I'm sure there is quite a lot missing.

But that's probably fine, Theia seems to be focused more on the current audience of Eclipse which is vendor tooling (chipmakers, FPGA, custom toolchains) rather than being an editor you are supposed to use by itself.