As a software developer who later got into hardware design, I've always been pretty disappointed with the quality of HDL tools. You get a bit spoiled by the quality of compilers like gcc and clang, and then you run into ridiculously expensive closed-source SystemVerilog compilers that fall apart on valid and obvious code, can't be run in a build farm, and which report cryptic messages for errors. So I've been working on my own open source SystemVerilog compiler / frontend for a while now, and it's nearing 100% completion in terms of language support.
https://github.com/MikePopoloski/slang