Focused mainly on one or two technology stacks (e.g. everything to do with developing a java application), with no experience outside of it

Nonsense; depth of knowledge is as important as breadth of knowledge. Ability to justify 50 different buzzwords on one's resume doesn't make someone a good programmer. It is a lot better to talk about the problems the candidate has solved, than the technology used to solve them.

Don't agree at all; not much use having a faint grasp on lots of different things if you're not able to choose (or be given) one in particular and to get on with the project. Even having in depth of a single language / technology / whatever puts a developer in a much stronger position when it comes to doing something else similar-ish - you have that sense of direction that only comes with experience. Although years of in-depth Wording did me fsck all use getting used to that nasty ribbon thing in Office Latest :-(