You're never going to get the straight story about anything unless you live it and breathe it, or know an honest no-bullshit man who will tell things you to straight up. The people who write about city venues are huge dorks, think Yelpers - they're never going to give you any real talk.
DTLA has lots of homeless people. Ask pretty white girls why they don't go downtown, and this is what they'll say.
Bars are close enough to walk to, but you'd be walking easily a mile or two over the course of a night if you bar hop. The streets in between bars are often dead and dark.
The people who go downtown, like thedude said, are the C-team. The A-team is in West Hollywood and Hollywood, or at a house party or a nice restaurant on a weekend night. Even cute white girls I meet who work downtown, who have every reason to live there, often live in West Hollywood. The dorkier she is, the more likely she is to live in DTLA.
For whatever reason, people who come from out of the city to party, the Bridge and Tunnel crew, mostly stop at downtown. They get too intimidated by the trendier places. Hipster bars are great, because the bridge and tunnel types feel least comfortable in hipster joints. Plus the B&T crowd are mostly non-white, and to me, either Asian (who I don't dig) or ugly. I'm actually fucking a Latina I met downtown, but most of the Latinas are busted, chicks you'd never want to be seen in public with, especially at the Latino-heavy joints.
People like to talk up the diversity of DTLA, but a lot of the joints are dominated by one ethnicity or another. The Mayan is all Hispanics (mostly troglodytes plus a couple hotties who are probably dating gangsters), the Belasco next door is all Asians. Hollywood is like this too I guess. Thanks to its diversity, macking downtown feels like a game of Where Is The White Girl?
Thanks to USC and FIDM, downtown does have some talent. I have two favorite bars in the city right now based on recent results, and one is downtown. I have banged a FIDM (fashion school) girl from going out downtown.
Co-sign everything the dude says. I actually hadn't thought of that or noticed that, but it sounds true. If you tried to open up a high end club in Downtown, it would become an ethnic minority haunt pretty quickly I'd bet. You'd have more luck with Thai Town or Los Feliz than downtown perhaps.
The Houston brothers have opened up a bunch of successful bars that attract talent, and they have yet to put one downtown. That's not a vote of confidence in DTLA's appeal. They have bars in East Hollywood, East Hollywood (La Descarga and Harvard & Stone), Hollywood, Hollywood, Hollywood (Pour Vous, No Vacancy, Dirty Laundry), Koreatown (Line hotel) and Marina Del Rey (in an Italian restaurant).
There are warehouse parties/raves downtown, I went to one last week. Not my scene, but I'm sure some will enjoy it, and fun for what it is. They're 'underground.'
To enhance downtown, the first thing I'd do is take care of the homeless. Put them in a shelter, arrest those who refuse, move them somewhere else, something, there's no reason they should sully the streets there. Downtown isn't Venice, it can't be full of homeless people and still look cool. to take it to the next level though is hard - it'd require attracting some hot chick job/industry magnets to the scene. WeHo and Hollywood have the entertainment industry, the Westside has the beaches, DTLA has... trains and architecture?
Downtown would also benefit from a more centralized nightlife scene - instead of a bar for every square block, put ten bars on the same street. Then again, thanks to ethnic segregation, the effect would be muted. So the bars would have to have similar demographics. The Mayan and Belasco are right next to each other, but virtually no one goes to both, I'd bet.
The funny thing - I was just walking around during the day near the beach, and I see way more talent than every bar I've been to in LA. Only high end clubs beat what you'll see walking around during the day in the hot spots. Yes, in LA Sunday brunch spots have more talent and better ratios than the bars.
A cause for celebration:
White Girls Are On The Way!
Whole Foods is opening a store in DTLA in 2015. This is what DTLA needs to get some talent, not some weesh Target. My main wingman, from this forum, lives nearby and is rather excited about it