Just the Eclipse legacy and development approach perhaps. Eclipse is 24 years old and its codebase stems from VisualAge before that, so I imagine it's ... idiosyncratic. Probably the most successful thing built on OSGi, though I dont imagine Theia brought any of that along.

At least for a while, Eclipse seemed like an Architect Astronaut's happy fever dream: actual bits if implementations hidden behind 5 to 10 nested interfaces and facades wherever I looked. I remember that at one point that I wanted to debug some weird behavior in the Plugin Development Kit and after sinking about half a day into exploring the source code, I didn't even see a single line of code that was actually doing anything meaningful. It was quite shocking to my old junior level self.