Indeed. Java is sufficiently dynamic/decompilable a game written in it can be heavily modded without adding specific support. C++ is much harder (depending on the game engine), though not impossible. If you do add modding support then everything is much better regardless of language, though (see Factorio, written in C++ and with a huge modding scene, because it was basically written with modding in mind. Lua is certainly helping with that, of course).