Participation doesn’t require a particular design. But a particular design can prohibit participation.
I interpret this quote to mean that it is a dashboard designer's responsibility to ensure people of different audiences can interact with your dashboard. Below I talk about some measures we can take to ensure that everyone can participate in the Tableau community.
1. Consistent Design
Are you designing a suite of dashboards which will be used together? Then try to use the same template for each dashboard. This way, a user only has to learn to interact with one dashboard before they can take insight from your charts. It also minimises the possibility a user will be overwhelmed by the cognitive load required to switch between pages. For example, use consistent fonts and always place the filters in the same position.
2. Minimise the Digital Ink
This will also help with keeping a low cognitive load. Keep the number of charts on the screen at any given moment as small as possible, and take off any unnecessary lines or labels (I think labelling bars and removing gridlines and axes looks nice). Now the user can focus on the message you are trying to convey with your charts.
3. Choose Text Thoughtfully
Text can be a super powerful tool for helping people understand the insights you are trying to provide through your dashboard. Start by choosing a font style people can read easily. This means using at least 12pt font size, a font which is easy to read (think Arial, Helvetica, Verdana) and which is a colour which contrasts well against the background.
The content of the text is also important. Avoid using unnecessary jargon and use plain English. Captions can also be used to not just explain the content of the chart but also the story - these captions are also picked up by screen reading software for visually impaired users!
Titles can also be used to guide the user through the data story. Try using descriptive titles instead of questions. So instead of, "how did flu numbers change in the past 12 months?", try "Flu cases reached peak numbers in December 2022".
Last in this section is mark labels. I've already mentioned using labels on bars to reduce screen ink, but also consider somebody who doesn't process shape or size in the same way you do. Labelling the bars means people can still see the different sizes of the bars.
4. Double Encoding
We're frequently told that double encoding is not "best practise", but this may be the easiest way of conveying a message to a neurodivergent individual. Providing two inputs means that is one doesn't work for one individual, another might. Consider a line chart with multiple lines: if each line is a different colour then someone who struggles to process colours may struggle to understand this. Overlaying different shapes onto each line may help this person use you chart.
(Note for Tableau: legends which show shape, size and colour would be a fantastic addition!)
5. Testing and Feedback
I am not a neurodivergent person. So while I've provided some guidance here on what might make your dashboard more accessible, you should definitely consider your audience. If your dashboard is for a business use case, ask different people who will be using it to take a quick look at your work before publishing. And remember, Rome wasn't built in a day: don't get offended if someone wants you to change something.