Oh dear. The issue isn’t the brute force, it’s that the online services leak and get cracked. And in an instant a single script takes the newly discovered username password combo and starts hammering it into the top 10000 websites, all within moments of the leak data becoming available.
Your super secret favourite phrase is worth crap once leaked alongside your email address.
Further don’t choose Microsoft for your Auth app, Go with an open source option, maybe one that encrypts and syncs so you have multiple devices just in case.