This is fair for certain languages like JS or Java (IntelliJ is amazing), but not as much for less popular languages. I started learning Rust a few years ago, where the Rust plugin for Jetbrains IDEs was still in its infancy. Switching to VSCode specifically for rust-analyzer was a great decision for me, due to the amount of tooling included.

VSCode is popular because it is easy to learn for a beginner and shares much of the language server tooling with Vim and other popular editors. If you write a language server, it can work across multiple editors like VSCode and Neovim. (Though not Jetbrains IDEs, as far as I'm aware.) Writing a plugin for Jetbrains will only work for Jetbrains, so there's less incentive.

While Jetbrains have more powerful IDEs for specific languages, its less popular when VSCode, Vim, Helix, etc. all work together.