<I>You contradict yourself a bit, since demand is high on the Westside, and if suffers from much of what you say is lacking in DT: little streetlife, wide boulevards, sfh's with low density, uninspired architecture. You may be mistaking what is coincidental or even subsequent to thriving areas with what is essential.</I>
The Westside has a huge anchor: the ocean. Its cooler [in summer], less smoggy and has great beaches. Its a significant, competitive advantage to downtown and can't be ignored.
Plus, I believe it was you or someone else who mentioned that in the distant past, LA drew people who were not all that deeply committted to urbanity. And when it did draw people who were into urban living, they tended either to leave or to end up settling and accepting the sprawl. Truly, I can personally relate to tommaso's rants. I made similar complaints when I lived in LA.....not about the shopping and stores but about everything else.
However, I believe the Westside's competitive advantage is changing for several reasons. The Westside has become overly congested and too, too expensive for the average new person moving to LA. And because of its sprawling nature, mass transit can't do much to alleviate the congestion.
Furthermore, over the past 2-3 decades, Americans, in general, have become more urbane......there have been tons of articles talking about how people are moving back into the cities. Cities that hadn't grown their population in decades are starting to grow again.
Hence, many new people moving to LA frequently can't afford the Westside and are turned off by its sprawl. It used to be Los Feliz, Silverlake and bottom basement Echo Park provided an alternative but even these areas have become fairly expensive. So, in some ways, downtown is winning by default.
In addition, smog is not nearly the problem it was for the LA basin, including downtown, that it once was.
So the only place you can find a truly urban experience is downtown. And adding impetus, downtown is the focus point for mass transit in metro LA. All trains lead to Rome......I mean LA.

The Westside can never compete with that decided advantage as it can't compete with the raw, edgy atmosphere that exists in downtown.
<i>What is essential is that none of this happens unless there is demand to live and work in DT to begin with. Demand brings the money; making the sidewalks wider or narrowing the streets does not. 5th Ave; Champs Elysees; Unter den Linden; Park Ave. are very wide streets and yet manage to attract. And ultimately, demand is driven by safety, clealiness, schools, low taxes, repaired sidewalks and streets, etc. Tourist attractions and business are fine; but if there are bad streets and crime issues, people will move somewhere else and commute to the work and attractions, just as they did DT for the last 60 years.
So here's to a cleaner, safer, medium rise DT without institutional block-busters. </I>
IMO demand is created when people want to be there. You could turn downtown LA into disneyland and if no one likes it, it will bomb badly. Actually, I have a better example. In reading the posts on this thread.......its clear that some restaurants open downtown, do well for maybe for a few months or a year, than close while others survive and continue to thrive. LA people like new things......its in their DNA. So anything new draws their attention.......esp if its uniquely cool.......like a new, hip restaurant in downtown LA. However, the hipness wears off fairly quickly and if there is no substance beyond the opening buzz, people lose interest and demand dies....hence the revolving door for some places.
So yeah, all the things you cite are important but in the end, they have to come together in ways that people like or demand won't be there. And if you create demand and get more people coming into downtown LA, and the area continues to grow increasingly vibrant, more companies like Gensler will relocate their offices into the city and everyone wins.
As for Champs Elysee or 5th Avenue or Park Avenue [I would not put Unter den Linden in the same category.....its too soon], those are streets that have a certain international caché which has developed over the decades and has given them a certain staying power. They are unique and rare in this world. And even with that, those streets over the years, have run into trouble partly, I believe, because of their long blocks and wide streets. In fact, some time during the '90s, the Champs Elysee was falling on bad times and required some gov't intervention to keep it on top.
Watch how people walk on a city street when they are not in a hurry. They stop and look, then walk a few more feet and then stop and look again. People want to be stimulated.......long distances act as dead zones and are a turnoff....all IMO of course.
Besides, I am not saying narrow all streets downtown. This country and LA still have a love affair with the car. In downtown LA, there are streets like Fig or Olympic that need to keep things flowing. Just narrow the streets that most cater to pedestrians. Many world cities have at least one walking street......and while I am not suggesting closure, I do think narrowing streets like 7th and Broadway would draw even more people to those streets.
In fact, I could see the intersection of 7th and Broadway becoming more of a center for downtown than Pershing Square. And don't get me started on Pershing Square.......I think the latest redo was done just before I got to LA or while I was there. IMO it was pure, unadulaterated crap. I wanted to graffiti that purple block in its center. Another opportunity lost...again IMO.
Thanks for the comments. Its been a while since I have had this kind of conversation.