YouCompleteMe isn't that hard to install, and it has been quite stable for me, I've migrated from clang_complete to YouCompleteMe years ago. One thing I agree, it's indeed bloated with a huge commit history, many internal dependencies and support for many languages you may not care for but still will end up cloning its associated submodules. That, that's an issue with YouComplemeMe, still.... it does the work.
I've worked on a fork with special purpose to better support C++, you may check this gif showing it off:
It leverages new parameter information that Clang is able to provide, you may learn more about this from this article of mine: http://nosubstance.me/articles/2015-01-29-better-completion-for-cpp/.
I don't use this anymore. coc-clangd is much better and simpler.