Charles, that is a most depressing but sadly believable account of the centro business district. You mention 3 major remodels downtown... I can think of 2 - the unnecessary Plaza Sol monstrosity that kicked out the popular Flea Mkt and the sidewalk/street parking revamp. What is the 3rd? When I was there in Sept I was actually shocked at how many empty store fronts, For Rent/For Sale signs I saw on my walks around town... lots of vacancies. Just read that the El Foco restaurant has closed on 5. I'm surprised you didn't mention the Pigeon Hotel ruin on the plaza as well. One thing I notice is shop after shop selling the same tourist junk - diversify, people!
The only thing we tourists can do is support the places we like downtown by spending our money there. I try to do my part: I stay downtown. I prefer the old Mercado to Mega (but go there & Chedraui too), I patronize the independent bakeries (Zermatt & the Cozumel) rather than Mega and Ched's. My dive shop is downtown. I get my pedicures downtown. When I'm not eating at friend's houses I go to restaurants downtown. Going with friends to El Centro cantinas with botanas is a must. I found a nice local photographer that made prints from my digi card near the old Mercado and also bought some flowers to celebrate a birthday from a shop in the floral neighborhood near there too. Went to Farmacia Dori. That's actually part of the fun of going there for me... doing 'errands' and feeling like I live there.
Good luck Wolfie... please do your homework.