as much as it is technically possible to easily and fairly accurately translate most major languages on the fly these days, and for short (read: a week or less) trips it's certainly more efficient to do so, for anything beyond a couple weeks of travel, or if you spend any amount of time around people of different nationalities/ethniticies, and especially for those who live in countries whose dominant language is not their own, it's absolutely worth learning the language.
can you accomplish most basic survival tasks without fluency in the local language? absolutely!
can you effectively connect with people and build relationships and community? outside of expat communities, almost certainly not.
and even if you manage to find enough locals that speak your language, or you're able to communicate through a third common language (english, french, etc), it will never be the same quality or ease of communication as it would be if you spoke their heart language fluently.
one thing that i've learned from speaking to people from many different languages is that speaking to a person in their home language has a different emotional weight than speaking to them in another language, even if they speak it very fluently.
this is of course anecdotal, but the number of times i've been able to instantly make friendships with strangers simply because i spoke their language rather than trying to speak to them in english or french or what have you probably counts for something.
language is of course deeply connected to culture as well - having a connection, or even any level of interest in a person's language instantly builds a foundation for further relationship in future.
certain languages have a reputation for being difficult; whether deserved or otherwise, if that's how the general population perceives them, it's virtually impossible to change their opinions.
one's language is closely linked to one's identity.
as such, native speakers of "difficult" languages understand that for outsiders to learn their language, it must have taken tremendous amounts of time and effort, and the majority of people around the world really appreciate that.
- native speakers are not teachers