OTOH:
1. it encourages the main company to simplify and/or extend the plugin API to make writing plugins v simple, or even possible in the first place.
2. it gives a smoother path for the inclusion of new trending technologies into the IDE.
3. it encourages devs to offer improvements to features that aren't high priority for the large IDE company.
For the latter, I'm thinking of Lombok support which, via a plugin, is much better in VSCode than it is in either Intellij or Eclipse.
Studying how the IDE made use of Turbo Vision was a good introduction to OOP ideas.
Also, many things in VSCode can be done in-proc as well if one so desires, including debuggers and language servers. Most extensions do them out-of-proc because it gives them more flexibility (esp. wrt implementation language for those components), and because it's easier to test such isolated components.
The disconnected VSC model - main company in charge of the editor, and third parties in charge of certain language plugin[s] - puts some languages' support at risk of being insufficiently developed.
I "only really want advanced editing + syntax highlighting + language server", and use VSC, but, while its support for "statically typed languge #1" is ok, the support for "dynamic language #2" is atrocious, to the point of being unusable (poor "go to definition", editor aggressively misaligning lines of code, etc.). I'm not sure it will ever reach sufficient support.
On an IDE, this doesn't happen, because the developing company must, within a certain qualititative extent, take care of all the functionalities.