I agree, it looks like JB are working on upgrading the default runtime to Java 17, but I think generally they could encourage developers to try out different runtimes anyway and report bugs rather than warning so strongly against it. I understand the JB runtime made some improvements to UI stuff, certainly the font rendering is much better in it, but at least for my setup that's not a big issue compared to things like indexing time. It'd be interesting to see a comparison of using different runtimes for IntelliJ, with proper profiling and the like.