Conference ranking and other forms of bibliometrics are stupid, but it’s the best we have.
Why stupid? Because there are drastically lopsided counter-examples, like van Wijngaarden grammars (a very important milestone in software language engineering, formalisation and documentation) or Wadler’s expression problem (another important milestone in software language engineering and comparison across paradigms), which were published in an internal report and on a mailing list, respectively. On the other side; there are also examples of papers published at highly prestigious venues that nobody ever cites — or, more importantly, which results nobody ever needs.
Why is it the best we have? Because even though it can be awkward and embarrassing to distill a person or a series of conferences down to a number, we cannot deny that there is some sort of hierarchy in the academic world, and total number of papers, citations, the h-index, etc, correlate with it.
Personally, it is an important instrument of reflection to look back at past publications, investigate and realise their ranks, track and assess your own path, while keeping in mind that it can still be wise to target a specialised lower rank venue over a high rank one where your audience is scarce. This page serves to explain how I estimate the rankings used in the list of my publications. In short, I use CORE for everything it knows about; SJR for journals and Qualis for conferences not found there. The last one is neatly accessible through Conference Ranks.
