3 Taylor Heinicke is a limited quarterback
The version we saw of Desmond Ridder against the Jaguars and Lions would easily be replaced by veteran Tayor Heinicke. However, the quarterback that showed up against the Texans is easily superior and made plays that Heinicke simply isn't capable of making. The issue for Atlanta with turning to their backup quarterback is they must be incredibly sure Ridder isn't the answer.
Even an outside quarterback like Kirk Cousins, Carson Wentz, or Matt Ryan would have to come in and build chemistry and learn a new playbook. Atlanta's options are limited and bringing in another option would only be a desperation move or due to injury.
Heinicke is a great quarterback for Arthur Smith's system and would have been a better option than Marcus Mariota was last season. But the ceiling for Taylor is far lower than Desmond's as is the bust potential. Heinicke is the boring but safe option Atlanta can turn to only if they are completely sure that Desmond isn't the answer.
As pointed out before Arthur Smith gets to that point only if Desmond is turning the football over at an incredible rate and leaves the head coach no choice.