This is true, but if their password database gets compromised and they're using insecure storage then they can brute force all day. There are server farms dedicated to doing just that and the vast majority of users are using simple, easy to guess passwords. The most common password? "password" [source: https://nordpass.com/most-common-passwords-list/]. Yes, we are a stupid species.

Nobody will try to brute force your account on a login form unless you are a high value target. Databases get leaked and password hashes with them. There are tools like haveibeenpwned which check your email against known database dumps that are available to everyone on the dark web.

In theory that is correct. In practice, not always the case. Up until 8 years ago you could brute force iCloud passwords: https://www.intego.com/mac-security-blog/apple-patches-brute-force-password-cracking-security-hole-in-icloud