Still no way to change Myriad Pro from being the default font?

What's wrong with Myriad Pro? You should be glad the default isn't Arial!

Arial stinks! It's just ugly, IMHO. It's a Frankenstein's Monster of fonts. Start with Monotype Grotesk, stir in some Akzidenz Grotesk, throw in the metrics of 1957 Helvetica, maybe a few other cues and you'll have this crooked looking sans thing. I've never liked it. And I've grown to really despise it for Arial's rampant misuse on designs of outdoor signs as well as a lot of other cooked up amateur graphics. When I see type artificially distorted (squeezed or stretched) out of its normal, balanced proportions I'm usually seeing Arial used in those examples of "font murder."

Balanced against that, Myriad Pro looks pretty beautiful. The typeface might seem a bit like a Frutiger knock-off, but Myriad has its own identity. I think it's a little more friendly looking than Frutiger (or Frutiger Next). Unlike the crummy default Arial, the Myriad typeface has variable versions. One is bundled into Adobe Illustrator. Another is available to sync at Adobe Fonts. 

I had this description saved, maybe this helps:

To change the default font you need to change the New Document Profile that you use to base your new documents on, like Print.ai, Art & Illustration.ai, Web.ai.

Open the profile you want to modify from:

Mac: (User)/Library/Application Support/Adobe/Adobe Illustrator version number/language folder/New Document Profiles

Win: C:\Users\....AppData\Roaming\Adobe\Adobe Illustrator version number Settings\language folder\x64\New Document Profiles

Open the Window > Type > Character Styles panel.

Double click the [Normal Character Style] and change the font in the Basic Character Formats.

Save the file.

You may have to save the file to your desktop first and replace the original after that.

I prefer to have set my Preferences to Use legacy “File New” interface to make it easier to select the presets.

Edit the Default Character style and save that as a new document profile.