A large portion of problems of using Eclipse CDT is that the Language Setting Provider is NOT properly set. See the MDN article mentioned in another comment for

A large portion of problems of using Eclipse CDT is that the Language Setting Provider is NOT properly set. See the MDN article mentioned in another comment for more on this. CDT parser is NOT bound to any build system. You can make it work with almost any build system, provided the build system had legitimate command line output. And CDT's performance is better than most of the LLVM/LSP-based tools. LSP based solution has not matured enough to be a real competitor. I remembered that around 2011 I've tried Qt Creator, and it was a bad experience since I did know how to cope with several build systems. I've no idea how QtCreator's multiple build system support is now. For the same reason, CLion is not good enough to compete with CDT. LLVM/LSP/Vscode/CLion, these are all exciting and have a lot of fans. Unfortunately, none of them is good enough in this subfield.