I am a bit surprised by this, as I had the opposite experience. I find ANTLR grammars much more maintanable than the hand-written parsers I encountered. Indeed I was asked to port hand-written parsers to ANTLR for maintanability. Also, ANTLR4 seems to me to produce grammars which are clearer than ANTLR3.

The weak point is error recovering, in my opinion. While ANTLR offers a sort-of-decent error recovery strategy for free, one has to customize it if they want to get great error messages.

I think that many maintainability issues are due to poor usage of ANTLR. What we do is to: 1) Limit semantic actions 2) For complex languages do tree-transformations, after parsing

With this approach we got pretty decent results.

Personally I find hand-rolled parsers too costly to build and harder to maintain, but I have limited experience with them. I guess it also depends on the context: if you are designing a DSL while writing the parser you want to be able to evolve it very quickly and in that context I think that a parser generator is very useful. If instead I would need to build an industrial grade parser for a general purpose language, having a large budget, then I would go for an hand-rolled parser