"Apple Mail account"? Do you mean the macOS Mail app?
Back to the OP's issue…it's my understanding that the macOS Mail app doesn't move anything to the Junk folder if you don't have "Enable junk mail filtering" checked in Mail>Settings…>Junk Mail or have a Mail app rule that moves email to junk.
If that's the case, the junk/spam filtering is happening at the server level. You did say you have no rules at the server level. You didn't specify, exactly, which provider you're using. Those would be the folks with which to compare notes.
Having said all that, Apple Intelligence currently seems to be throwing a wrench in the works…marking messages that are spam/phishing, and haven't been filtered at the server level, as "Priority". Who knows what other stupid things it is doing?
To test what's happening before you check your email with the Mail app, leave the Mail app off and access your email for a while via the web interface at your provider. If "most of the emails" are being marked as junk then your issue is with your provider.