Like it or not, San Diego is already the 2nd most expensive city to live in, relative to income. Also, like it or not, San Diego is desirable and more people will move here, especially well off retiree. So, you really have two option, continue on the same path of suburban sprawl or increase density and build for what is to come. Keep in mind that San Diego is almost built out, so if we continue down this path, we’ll be completely built out sooner rather than later. Which mean that it will only get more expensive to live here once San Diego is completely built out and the baby boomers are hitting retirement age in earnest. We also have heard it here many times that the economy are not very vibrant here and that many are moving to LA or bay area for jobs. Some of us would like our kids and grand kids to be able to stay in San Diego and have plenty of opportunities. In order to have that kind of vibrant economy, you need a lot of people, a lot of universities, and a lot of venture money. We can’t control the venture money, but we can control where people live, how many people actually fit in the city/county and how many Universities are in this region.
So with that said, to answer the question of why San Diego need to emulate denser cities in order to be “world class”, because that’s just a natural progression of a world class city. It grows. As it grows, you can either build more housing for the new people or have them be priced out and only the rich and those who bought ages ago can afford to live there. I would much rather start building density today instead of decades down the road when you paint yourself into a corner. Personally, I think Pacific Highland Ranch would have been a much smarter place to build such density and town center. But too bad that didn’t happen.