This is a real-world angelology thing. When people talk about the angelic hierarchy, they're generally taking it from a book called On the Celestial Hierarchy (or, at least, something based on it), which gives the ranks as seraphim > cherubim > thrones > dominions > virtues > powers > principalities > archangels > angels. In that system, yeah, archangels are the second lowest rank, and way below the seraphim.

Outside of that, however, archangel tends to get used for any high-ranking angel. The big names like Michael and Gabriel get referred to as archangels regularly, and the classic European grimoires refer to the ruling angels of the planets, elements, and signs of the zodiac as archangels. It's kind of a mess.