Is there a way to change how often Intuit sends insanely numerous emails that are just marketing.

You can't change the frequency, but you can change your email marketing preferences on the Preferences page of the account manager. If you use TurboTax Online, open a return and select Account Manager from the bottom of the left side menu to get there.

Or you can use this link: https://accounts.intuit.com/app/sign-in?&redirect_uri=https%3A%2F%2Faccounts.intuit.com%2Fapp%2Faccount-manager%2Fpreferences%3FofferingId%3Dintuit.tax.ctg.canada.turbotaxonline%26rgn%3Dca%26prgn%3Dca%26loc%3Den-ca