How about this?

data = Table[
   RandomVariate[BetaDistribution[2, RandomReal[]], 100], {4}, {2}];
DistributionChart[data, ChartLegends -> {"False", "True"}, 
 ChartLabels -> {{"0-9", "10-19", "20-29", "30+"}, None}]

for the 2-level bar chart in update 1, using a legend for the bar colors for True and False would allow you to use the age group labels along the horizontal axis. Here is a simple hack of your BarChart that accomplishes this:

BarChart[First /@ visualizeThis, Frame -> True,
 FrameLabel -> {"age", 
   "percent of subgroup sick during given time period"},
 PlotTheme -> "Detailed",
 ChartLabels -> {Rotate[#, Pi/2] & /@ Last /@ visualizeThis, None},
 ChartLegends -> {False, True},
 PlotLabel -> "# of people sick in time range in a given age group"]

update 1 (notebook attached): I have my first visualization, although it needs some better generalization into a reusable function for numerical demographics. I also need some better styling guidance.But a good night's progress on a very sizable (and imo important) task. Hope to see some others able to engage here, I know my prompt might be too abstract or vague, ask questions if you want to.

Attachments:

covid-viz.nb

Holy moly that is cool, I didn't even realize distribution chart was a thing! Thank you! Will start working on one of those. I just added a much cleaner data set and some starter code that I will begin working on to produce visualizations for one given action. Attaching here as well

Attachments:

simple-starter.nb

Thanks Bob, that looks much cleaner! I have not played with charts and really appreciate the tweak.