The thing is, making it so that you could exchange dungeon keys for scen keys would probably lower the number of people who use the AF even more. It’d reduce the incentive for people to use the AF, which is a bad thing long term. Solo play is good to have, but the social aspect of the game is a bigger hook to keep people playing.
If English isn’t your first language, a good cabal can be harder to find. That doesn’t mean that you can’t find other people who share your language though - there are non-English speaking cabals out there, and you don’t have to be in a cabal to do stuff with people, it just makes it easier to find others with similar goals.
You get as much out of a cabal as you put into it. If you join one then just sit in silence and don’t join in, then you’ll benefit far less than someone who takes part in the chat. Most good cabals aren’t too concerned about people’s english skills - if you have enough ability to make yourself understood, that’ll do. It’s also a good way to develop your language skills, I’ve played with many people who joined in part to help practice their english, and it’s always impressive to see how much they learn!
Auto accepting groups isn’t a good system, because then you get zoned in to dungeons with people who are AFK. Starting a dungeon without a full group can suck too, if you’re low on damage then you can find yourself stuck waiting, unable to do anything until you get your 5th person. Or if you’re the 5th person and you zone in to find that several of the bosses in the dungeon are already dead, then you’re going to have to go through the AF queue again to use up the keys that you have left over. It all just adds to the frustration.
I can understand your reasoning - it’s annoying to have an unused resource when it could potentially be swapped for another. But part of game design is finding ways to motivate people to take part in group activities. They’re unlikely to introduce something which would undermine that goal.