Increase Font Size of List Web Part

TheWhiteGoose99 if you're using SharePoint Online, navigate to the list page and then select a column you want to change the font size to Column -> Column Settings -> Format This Column, a window appears on the right, Click Advanced Mode, and a text box appears for you to enter JSON code to manipulate the HTML. Copy and paste the Code snippet below into that JSON text box.

{
"$schema": "https://developer.microsoft.com/json-schemas/sp/column-formatting.schema.json",
"elmType": "div",
"debugMode": true,
"txtContent": "@currentField",
"style": {
"font-size": "18pt"
}
}

You can change the value "18pt" to whatever you want. The formatting settings will carry over to the Web part. Here's a https://docs.microsoft.com/en-us/sharepoint/dev/declarative-customization/column-formatting to more JSON formatting if you're interested. 

Edit: I realize that you said you were utilizing wiki pages? This method will work with Modern list pages. (Tested)