Second most dangerous city in the world. You got lucky. It is foolish to advise people that Tijuana is safe.
* Upon arrival at the bus station I ask staff if they can recommend a safe route for me to cycle (I had a touring bike) the several km to near the US border. They say the center is safe, the bad barrios are elsewhere, and it was a bit silly that I would even be worried.
* I ask the first police I see the same question and get the exact same answer.
* I am occasionally passed by lycra-clad locals on expensive bikes. Here and there I see a lot of conspicuous American tourists of the fanny-pack variety walking around, mainly elderly. These are the sort of things that would not be done if people had to fear for their lives.
* I go into an Oxxo for some snacks and ask the clerk about safety. He says it hasn't been a concern in that central area for a long time now.
* I stand in a queue for two hours to cross the border. The people around me in the queue, Mexican and American alike, say safety hasn't been an issue in the city center for a long time now.
That is a difference from a couple of decades ago, when one was warned about even the city center and even in daytime.
Mexico is a beautiful country but it still has its problems. You've just kept to tourist areas if that's your view on it.
I spent last winter cycling the length of the peninsula, avoiding the highway. Didn't see a single touristy place until a month into the journey when I reached San Ignacio and Mulege. Then didn't see another touristy place again for weeks until La Paz.
On a previous trip to Mexico I cycled the length of the mainland from Mazatlan to the Guatemala border mainly on unpaved roads. I am well aware of the country's challenges and the need to ask about safety conditions. I stand by my assertion about Tijuana -- if safety in the city center were an issue for tourists and people passing through, local people would readily tell you that and elderly Americans wouldn't be strolling around carefree.
> The first thing you see driving in to TJ are decrepit and destroyed buildings
That describes a considerable portion of the world, including places where safety is not a concern.