I beg to differ. I will speak personally here - calling Corona "mediocre" is something I find insulting, due to how hard we all work on the engine. Calling the caustics solver "terrible" I find insulting, due to how hard everyone worked on that and just how complex a topic that is.
I have yet to see you point to another engine that does it better - rather you point to some ideal situation that is likely not possible for any engine or any developers, where caustics are magically possible for every scenario while only adding a modicum of extra render time, and say that since it doesn't live up to that it's "terrible".
So, speaking personally, I am insulted by both of those comments, and the way they are delivered - not in a way hopeful for what improvements the future may bring and saying what you would love to have in there and giving pointers all while understanding the timescales and difficulties involved, but rather by simply denigrating what is there already. We're always open to suggestions for improvement, but calling something mediocre and something terrible is not a suggestion for an improvement, it is just that - name calling.