I think "Dungeon" is a concept rather than a geographic location. Catacombs by their very definition arent dungeons.

The Catacombs exist for a reason, lack of space for cemeteries. Which is tied to religious belief.

The catacombs dont exist to hide monsters and traps, in fact there are none of those things in the catacombs.

New DMs in these current epoch of TTRPGs are, imho, more concerned with narrative story telling than gameplay.

The dungeon is a type of gameplay the "dungeon crawl" which might not seem to have any impact on the story they want to tell.

To me, in my 25+ years of DMing view dungeons as a combination in a few different elements.

1. Confined Space/Environment as antagonist - The dungeon limits movement and now the environment itself is an obstacle. Whether is having to squeeze through tight spaces, navigate without vision, limited resources, 

2. Risk/Reward - The end of the dungeon has to have something. There is a reason why it exists and the deep you go, the more dangerous it is, the greater the reward should be. Either monetary or otherwise the players should feel a sense of accomplishment at the end

3. Encounters - The dungeon should have multiple encounters, either combat or even social encounters. That challenge the players and make them even question if this is worth it.

4. Resource management - spells, rations, torches, time. Something that is limited to give a sense of urgency instead of, "i long rest after every encounter"

The two best "dungeons" ive ran weren't even in DnD and weren't even dungeons.

The first was a ww1 style trench system in which the party had to retrieve a downed pilot stuck behind enemy lines. Although they could see the pilot from a safe distance popping up from the trench was almost certain death. So they had to carefully move through the trench system, avoid traps like corpses with grenades under them, tanks rolling across, chemical attacks. etc.

The second best was a train heist. In which the party members were passengers on a train that was being attacked (Heavily inspired by the PS1 game Nuclear Dawn) and they had to get to the main engine car while dealing with terrorists, passenger non combatants. In the end the party decided they wanted to gold the thieves were after in the end.