I am new to the microcontroler development and I had to choose an editor . Because I am fan of open source I chose Atom and not Visual Code even though you clearly mention that debugging is more flexible with Visual Code.
after downloading Atom I just install the package for platform I/O. Then I see this popup window telling that I shoud have preferred Visual Code. This is very upsetting.
As a consequence of this pop up window I cannot believe that you are independent and I have a strong suspicion that you have financial interest in the promotion of visual code may be through partnership or something else!.
Sorry you feel that way. If open source is what you want, there is nothing to stop you using VSCodium or self-compiling VSCode, as all the source is there on GitHub.
I believe the warning was added because more people are using VSCode than Atom, hence the priority will be to support VSCode in preference to Atom. I don’t think support is intended to be dropped (but the inference is certainly there in the name of the function displaying the notification -
maintenance.notifyExtensionIsDeprecated()), but it certainly isn’t going to be getting the focus of development efforts because VSCode is simply the more popular editor.