There is no imaginative marketing of all that Downtown might offer.... a huge missed opportunity for everyone. When I go to a cultural event, I end up in San Marco for dinner first, not Downtown. Where is DIA, DVI, Visitors Bureau, etc.?
What imaginative marketing are Town Hall, Taverna, Matthew's, and Rue st Marc doing to draw you in? In the 20+ years that Matthew's has been open, i don't think i've seen a single advertisement for them. Matthew's and Cowford have valet, but Bellwether is easier to park at than all other San Marco options. I'd argue that Bellwether and Cowford are on par with everything except Matthews, so why don't you patronize the downtown options more? If you'd like downtown to be more successful, why don't you prioritize supporting the businesses?
Places outside downtown, as you note, don't need to market much because they don't need too. They have a built-in customer base due to their locations and perceived ease of access and security vs. Downtown. I am not saying the perception is accurate but, as the saying goes, "perception is reality."
So, if you want to overcome a less than robust perception, you need to market yourselves. If marketing wasn't beneficial, we would not have any promotions, advertising, etc. so it obviously works. You can stick your head in the sand and wait for perceptions to change but then you may be out of business as so many Downtown places have seen.
By the way, the San Marco Merchants Association does lots of marketing for San Marco Square and is responsible for engineering the current traffic flow, upgrading the streetscape, updating the landscaping and hosting lots of events during the year (such as fun runs, Xmas festivities, art festival, Fla-Ga weekend, etc.). I would call that imaginative marketing and don't think San Marco would be where it is today without those efforts, in part at least.
Downtown has advantages, as I suggested, with the cultural arts, the river, etc. and it is missing the boat not to exploit those. Without promotion, they will be greatly overlooked by much of the populace, as evidenced by the current state of affairs.