How can I change my default email to google mail? It keeps defaulting to a provider from 8 years ago.

If you no longer use that email service provider, you can remove it from Mail.

Mail menu > Preferences... > Accounts

Select the unused Account and click the [—] (minus) button below the account list.

You can't set Gmail as a default. Clicking a link to send an email will bring you to an email client. You then configure that to your needs. But as Gmail is service not an app, it cannot be set as a default.

What app do you use for email? Gmail is a service you access via an app.