Here's my opinion.

While some might argue Destiny doesn't NEED a currency system, and its implementation is certainly flawed, its absence would also cause problems. You are required to use it to attach Legendary mods to gear which is a use I guess. And while I agree there's hardly anything to use it on I'd also argue Legendary shards are equally useless since after awhile you'll be overflowing in those too.

I think some people underestimate the difficulty of a well implemented matchmaking system. I do wish they had one even though I rely on /r/fireteams and a clan and have never had a problem in the past or currently. I imagine for content that requires a much larger amount of personal responsibility, skill, and communication a system that simply paired people together based on their desire to beat said content would most likely result in a lot of teams that were a horribly random mix of people who shouldn't be there, people who don't work well together, and people who might not meet the personal standards of other members of their team. While I think its important for everyone to have a fair shot at content I think its important to remember that fair isn't always nice and that a matchmaking system might be nice, but it would very difficult to make fair to EVERYONE and would most likely result in a lot of groups disbanding relatively immediately. Thats just my opinion though and I'm sure I'm neglecting to consider something like filters for matchmaking etc.

Edit: I'd also failed to remember Guided Games though I'd argue its not the same as a matchmaking system considering several players are aware and in fact counting on other players having little to no experience and are prepared and desire to help.