It's not polite to address someone older than you without using "san" or "senpai" etc.
It's rude to call someone who is your senior by their name only.
ーIt's not polite to address someone older than you without using "san" or "senpai" etc.
「年上の人を『さん』や『先輩』などをつけずに呼ぶのは失礼です。」
It's not polite to address ... で「呼ぶのは礼儀正しくない・失礼です」
someone older than you で「あなたより年上の人・先輩」
ーIt's rude to call someone who is your senior by their name only.
「先輩を名前だけで呼ぶのは失礼です。」
It's rude to call で「呼ぶのは失礼です」
one's senior で「先輩・目上の人」
ご参考まで！
カナダ 
アメリカ合衆国 
